To solve for the variables, we need to use invert operations to solve equations, addition ans subtraction are inverse operations as multiply and division are inverse operations, so let's start:
a.
7x+5=6x+2
7x-6x=2-5
x=-3
b.
12x+8=6x+2
12x-6x=2-8
6x=-6
x=-6/6
x=-1
c.
8q-5=-4q+7
8q+4q=7+5
12q=12
q=12/12
q=1
d.
2a-7=5a+8
-7-8=5a-2a
3a=-15
a=-15/3
a=-5