Since all angles in a triangle add up to 180 degrees, we can build an equation with the given sides.
75+x+53+x+68=180
Now we can simplify
2x+196=180
Subtract 196 from both sides
2x=-16
Divide each sides by 2
x=-8
Now since angle A is x+53, we have to add 53 to -8
53+(-8)=45
53+(-8) is the same as subtracting 8 from 53 which is 45
So angle A=45