*Sorry I messed up my math please read the new answer.
Use distrubitive property to get rid of parentheses. Multiply -3 by 4r and -8 to get -12r+24=36. Then zero out 24 by subtarcting 24 from both sides. You. should then have -12r=12. Divide by -12 on both sides to get r by itself. Your answer should be r=1*. Hope this helps :)