Need explanation for Blue Book Math, number 5, page 888, Test 9

Test Preparation
1

In the figure above (right triangle with legs marked ‘x’), the perimeter of the triangle is 4 + 2 times square root of 2. What is the value of x?

A - 2
B - 4
C - Square root of 2
D - 2 times square root of 2
E - 2 + square root of 2

I said C. It’s A, and I don’t know why.

2

If the legs are x, the other side (the long one) is x times square root of 2. This is something you should know, and it is in the info at the beginning of the section.

Then, you have 2x+ x times square root of 2 = 4 + 2 times square root of 2.You can see that x=2.

3

@Argentina2017 Oh, wow! I completely forgot about the 45-45-90 triangle rule. My mistake. Thank you for the help.