X = 7, Y = 16.
The bottom 2 lines of the kite are equal, so 2x + 5 = x + 12. Subtract x from both sides, and then subtract 5 from both sides. You end up with x = 7.
You then substitute (put it) this value for x in the top 2 lines ; x + 5 = y - 4. This would equal 7 + 5 = y - 4.
Therefore you add 4 to both sides and you get y = 16.