Answer :

8x-12 = 5+15
8x-12 = 20 
     8x = 32      +12 
       x = 4        ÷8

8x-12=5+15       Regroup
    +12  +12

8x= 5+15+12       Add like terms

8x=5+15+12

8x=32               Divide both sides by 8
/8    /8

 x=4 is your answer