If the average of x and y is 10, then the average of x + 7 and y + 17 is ?

Answer 1

(x+y)/2 = 10

(x+7 + y+17)/2
= (x+y + 24)/2
= (x+y)/2 + 24/2
= 10+12
= 22

Answer 2

note that this is also just

(x+y)/2 + (7+17)/2