45 : x * 100 = 900
45 : x = 900 : 100
45 : x = 9
x = 45 : 9
x = 5
160 × 5 : x = 100
800 : x = 100
x = 800 : 100
x = 8
824 - 240 : x = 800
240 : x = 824 - 800
240 : x = 24
x = 240 : 24
x = 10
245 + 50 * x = 745
50 * x = 745 - 245
50 * x = 500
x = 500 : 5
x = 100
x : 12 × 9 = 396
x : 12 = 396 : 9
x : 12 = 44
x = 44 × 12
x = 528
x * 16 : 5 = 1360
x * 16 = 1360 × 5
x * 16 = 6.800
x = 6800 : 16
x = 425