Răspuns:
a) 4(x+2) -3(x-1)= 12
4x +8 - 3x+3 =12
x+8+3=12
x+11=12
x=12-11
x=1
b) 4(x+2) -3(x- a) =12
4x + 8 -3a +3a =12
x+8+3a=12
3a= 12-x-8
3a = 4-x
a=4/3 - 1/3 x