>>351
(35*75)/100+25x/100 = 35.5
2625/100+25x/100 = 3550/100
25x/100 = 3550/100-2625/100
25x/100 = 925/100
x = (925*100)/(100*25)
x = 37


>>354
175+x/18 = 920-x/55
x/18+x/55 = 920-175
55x/(18*55)+18x/(55*18) = 920-175
73x/990 = 745
x = 745*990/73
x = 737550/73


>>357
中点は縦書きのとき以外は乗算記号に見えるから改善しなさい