Answer:
y = 7, x ≈ 9.9
Explanation:
The remaining angle has to also be 45° which tells us we're working with an isosceles right triangle, or that y also has to be 7 (the same length).
Use the Pythagorean theorem for x.
a^2 + b^2 = x^2
7^2 + 7^2 = x^2
49 + 49 = x^2
x^2 = 98
x ≈ 9.9