a × 42 + 720 - 720 : 9 = 1060
a × 42 + 720 - 80 = 1060
a × 42 + 720 = 1060 + 80
a × 42 + 720 = 1140
a × 42 = 1140 - 720
a × 42 = 420
a = 420 : 42
a = 10
100 - b : 16 + 350 : 7 = 144
100 - b : 16 + 50 = 144
100 - b : 16 = 144 - 50
100 - b : 16 = 95
b : 16 = 100 - 95
b : 16 = 5
b = 16 × 5
b = 80
