You would plug 15 and 21 into the equation provided so 15/21=x/100. You could then cross multiple giving you 21x=1500. You would divided by 21 on each side to isolate x. This should give you 71 and a super long decimal which is equal to 3/7. So the correct answer is 71(3/7)%. You could also just do 15 divided by 21 but that's to simple. Hope this helps!
