We can complicate things a bit more. The object the child is holding is tilted one to the right and one to the left, so we can conclude that one is positive and the other is negative, haha.
10 + (x + 4 - 4) * 4 = y
10 + (x + 0) * 4 = y
10 + (x) * 4 = y
10 + 4x = y
y = 4x + 10