x : 15 = 17 rest 7
x = 17 × 15 + 7
x = 255 + 7
x = 262
169 : a = 24 rest 1
a = (169 - 1) : 24
a = 168 : 24
a = 7
a : 7 = 143 rest 6
a =143 × 7 + 6
a = 1001 + 6
a= 1007
286 : b = 15 rest 1
b = (286 - 1) : 15
b = 285 : 15
b = 19
a × 16 =224
a = 224 : 16
a = 14
12 × a = 300
a = 300 : 12
a = 25
a × 7 = 756
a = 756 : 7
a = 108
24 × a = 744
a = 744 : 24
a = 31
