I solved 4, the answer is 11, seconds: 5x+4(x-3)=87 = x=11, but I don't know how to solve number 5, please anyone explain how to get it!! I'm begging!! GIVING EXTRA POINTS!! BRAINLIST ANSWER!!

I solved 4 the answer is 11 seconds 5x4x387 x11 but I dont know how to solve number 5 please anyone explain how to get it Im begging GIVING EXTRA POINTS BRAINLI class=