We know the bottom triangle is a 45, 45, 90 triangle, so the hypotenuse is √2 times the value of the legs:
(√2)(√2)
=√4
=2
Now, we can use this to solve for y. The top triangle is a 30, 60, 90 triangle. The side we found above is the side across from the 30 degree angle. The side opposite the 60 degree angle is √3 times the side across the 30 degree angle. Therefore, we can solve for y by multiplying 2 by √3
y=2√3