Question 807798
a + b = 19
a - b = 10
a = 19 - b
such that 19 - b - b = 10

19 - 2b = 10
19 - 10 = 2b
9 = 2b
4.5 = b

a = 19 - b = 19 - 4.5 = 14.5 

a = 14.5, b = 4.5