Its a rectangle so the 2 horizontal sides are even and the vertical sides are even. So, since one side is 10, the other side has to be 10. So, 2y+4 = 10. subtract 4 from each side getting 2y = 6. divide by 2 to get the y by its self and you get y = 3.
For the horizontal side, 10 + 2x = 18. subtract 10 from each side. 2x = 8 divide by 2. x = 4
