1 .
a+b+c = 126
b = 7+ a
c = b + 10 => 7+a +10 = c
a + 7 + a +7 + a + 10 = 126
3 x a = 126 - 24
3 x a = 102
a = 102 : 3
a = 34
b = 34 + 7
b = 40
c = 40 + 10
c = 50
2 .
(47 - a ) x 2 - 15 = 45
(47 - a ) x 2 = 45 - 15 = 30
47 - a = 30 : 2 = 15
a = 47 - 15 = 32