Ok, so the answer is 80%. How I got this, I did the cross-product method. On one side, I did x/100, and the other, I did 720/900. And I multiplied 720 by 100, and got 72,000. And I also did 900 Times x, and got 900x. So, the new equation is 72000 = 900x. I divided 72000 by 900, and got 80, which is the percentage. (Picture of Cross-Product Method)
This is a right triangle, so AC is a hypotenuse.
The other angles are each 45 degrees, so the legs AB and BC are equal length.
a^2 + b^2 = c^2
a = b
2a^2 = (5sqrt2)^2 = 50
a^2 = 25
a = 5
Answer: 5