Can someone please help me out?? I would really appreciate it.

The other angle will be 45 degrees ( 180-90-45=45 angle sum of triangle)
Thus this is an isoceles triangle—> x = y
Using Pythagoras’s theorem, 2x^2 = 7^2= 49
Thus x = 7/rt(2) or -7/rt(2) , then reject negative values and rationalise to get 7rt(2)/2 for x, thus x = y = 7rt(2)/2

i believe your answer is b.

good luck!

cutie~