Verified answer

a + b = 87 - сумма

a - b = 19 - разность

(a + b) + (a - b) = 87 + 19

2a = 106

a = 106 : 2

a = 53

a + b = 87                   a - b = 19

b = 87 - 53                  b = 53 - 19

b = 34                          b = 34

Ответ: а = 53,  b = 34