The angle across from the side with a length of 7 = 45°.....and the angle across from y is the same....so.....if two angles in a triangle are equal, so are the sides opposite those angles.....so.....y = 7
In a 45 - 45 - 90 triangle....the hypotenuse (x) = the length of either leg*sqrt (2)....so
x = 7sqrt(2) ≈ 9.9