Answer:
a = 20; b = 2√101
Explanation:
The triangle at upper left and the one at lower right are similar. Ratios of corresponding sides are equal, so ...
200/a = a/2
400 = a^2
√400 = 20 = a
Then, by the Pythagorean theorem, the value of b can be found:
b = √(a^2 + 2^2) = √(400 +4) = √4·√101
b = 2√101