The equation is 0.2x 0.3x a=0.15x (h/100)x a and you solve to get 0.06a=(0.15h/100)a.(Note that the h has to be divided by a hundred too). That becomes 0.06= (0.15h/100) then you divided that equation over .15 so the equation becomes 6/.15=0.15h/.15. The final answer should be h=40.