1) a x 42 + 720 - 720 : 9 = 1060
a x 42 + 720 - 80 = 1060
a x 42 + 720 = 1060 + 80
a x 42 + 720 = 1140
a x 42 = 1140 - 720
a x 42 = 420
a = 420 : 42
a = 10
2) 100 - b : 16 + 350 : 7 = 144
100 - b : 16 + 50 = 144
100 - b : 16 = 144 - 50
100 - b : 16 = 94
b : 16 = 100 - 94
b : 16 = 4
b = 4 x 16
b = 64
E = 100 x a - 10 x b
E = 100 x 10 - 10 x 64
E = 1000 - 640
E = 360