Replace

You live where it freezes? Replace it, fixes will not work.

You cannot repair that. Brushed concrete runs about $4 per square foot, and then factor in a cost for removing the old concrete.

Yeah if you want to play basketball on it, replacement is your only real option

Man, I'd replace the WHOLE THING not just this third. You'll be much happier with it.
Also, why did it fail like this? Tree roots? Bad drainage?

Thank you and yes, in north Texas, we get a few freezes a year.

A combination of both those things + age, I think. The tree has since been removed. Looking like replacement might be the way to go, but $$$....Thanks for the reply.

Get rid of the whole thing

That looks to be 2" thick. You should have 4" for cars.

And probably a good bit of draining rock beneat the concrete to limit the damage from freezing soil.

And drain it better

Not going to last, as mentioned by other commenters, but if you just want a fix for a year or two:

Rent a pressure washer, clean off the surface, all the cracks.

Make sure the surface is damp. Mix up a bag of ready to mix concrete, pour it on, level/spread it (screeding) with a 2x4. A large drywall trowel or something similar can be used to get a nicer finish.

About a $15 'fix'. And as the others say, in a couple years it will probably break apart.

We used 6" thick with the proper amount of rebar. This was 30 years ago and only have a few hairline cracks. This was for a parking pad.

If you want to fix it every year they just patch on top of it, if you want to fix it once, remove and replace, have to fix the base and drainage or it will just keep cracking

I've seen 4" recommended for cars and 5" for heavier vehicles. Obviously other factors go into the design and the local construction companies know what works for the area. When you had it done was that the only option or could you have gone thinner?

The contractor who did the job was a neighbour. He built my double garage 2 or 3 years before and wanted to bring the pad up to the same level as the garage floor. He said that it would stand up better to frost. Canadian prairie winters. The important part was the rebar. He laid the proper amount of rebar and I got the job of tying them together with the wire twisty things with the hooked tool. He was one hell of a contractor.

Replace, because of that dip, any repairs will be short lived.

What is the depth of the rock bed? 6", 8"?

All that old driveway needs to be removed, the bed will all be releveled, new bed of stone, etc.

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Yes it's big money. Wait until you see how expensive it is to throw old concrete away!

This is why concrete sucks. To keep it from cracking you need a ton of rebar and have it like 6 inches thick. So yeah replace it with a 6 inch slab with tons of rebar.

That is "not a crack". That is cracked and sunken concrete. Top coating will not be a viable solution. If you were to remove the "triangular" sunken area and replaced it somewhat on the same level as the area outside the triangular sunken area you will have about 20+ bags 60 lb. of concrete to mix and that is a lot. If the sunken part is thicker than 4 inches you just add more and more concrete mix and more and more labor. You need to decide to spend money on a patch that will always look like a patch or go all the way, which can be costly.

Is there a way to layer it with tiles or something similar?

It's cheap where I am (PNW). $20/yd to dispose. They grind it up into recycled road base and resell it for $30/yd.