156 - (45/x)* 21 = 51
156 - 945/x = 51
945/x = 156 - 51
945/x = 105
x = 945/105
x = 9
5 * (68/B) + 87 = 172
340/B + 87 = 172
340/B = 172 - 87
340/B = 85
B = 340/85
B = 4
256 / (45 - x/8) = 64/4
256 / (45 - x/8) = 16
45 - x/8 = 256/16
45 - x/8 = 16
x/8 = 45 - 16
x/8 = 29
x = 29 * 8
x = 232