3(x+2)-2(x+1)=8
you distribute the 3 to the numbers inside the parentheses as well as the -2 which gives you:
3x+6-2x-2=8
then you combine like terms which gives you:
x+6-2=8
then you subtract 4 from both sides to isolate x and you end up with:
x=4
Hope this helps!