-7x-3x+=-8x-8

the answer is x=4 

the first thing you do is 

1.combine like terms... -7x and -3x= -10x

-10x=-8x-8

2. isolate the variable ... add 8x to both sides

-2x=-8

3. solve... divide both sides by -2

x=4

-7x-3x+=-8x-8        simplify on the left

-10x = -8x - 8         add 8x to both sides

-2x = -8                 divide both sides by -2

x  = 4