Question

How to do the 10th one?​

Answer 1

$2xy = 70 \\ {x}^{2} + {y}^{2} + 2xy = {(x + y) }^{2} \\ 74 + 70 = {(x + y)}^{2} \\ {(x + y)}^{2} = 144 \\ x + y = 12 \\ {x}^{2} + {y}^{2} - 2xy = {(x - y)}^{2} \\ 74 - 70 = {(x - y)}^{2} \\ x - y = 2$