3/9=b/12
9b = 12*3
9b = 36
b = 36 : 9
b = 4
b/5=6/15
15b = 6*5
15b = 30
b = 30 : 15
b = 2
2/9=8/b
2b = 9*8
2b = 72
b = 72 : 2
b 36
10/b=30/33
30b = 33*10
30b = 330
b = 330 : 30
b = 11
