after effects slider control code help
The error message is telling you that you've got a stray bracket, so count your brackets and see if the (s match the )s. Spoiler alert: they don't.

I can see two cases: after each linear function call you have a closing bracket after the "Null 1" string that isn't matched by an opening bracket. And "Null 1" on its own is just treated as a string, not a layer, so that's another problem.

I'm assuming you mean thisComp.layer("Null 1") which is a reference to a layer. So

out = linear("Null 1").effect("Slider Control")("Slider"), 0, 100, 0, 2.5);


should be 

out = linear(thisComp.layer("Null 1").effect("Slider Control")("Slider"), 0, 100, 0, 2.5);