If the two quadrilaterals are similar
x/15 = 20/24
cross multiply
24x = 15 * 20
Divide both sides by 24
x = 15 * 20 / 24
= 12.5
To get y
y + 5 / 15 = 35 / 24
cross multiply
24 (y + 5) = 15 * 35
24y + 120 = 525
24y = 525 - 120
24y = 405
Divide both sides by 24
y = 405/24
= 16.875