Answer:
A
Explanation:
Both triangles are similar triangles!
Length 21 for the top triangle is similar to length 20 for the bottom triangle
Length 29 for the top is similar to b on the bottom.
Length 20 for the top is similar to a on the bottom.
Use the first ratio: 21/20 to find the proportionality constant.
Divide 29 by that constant to get b
Divide 20 by that constant to get a
You end up with b = 580/21 (= 27.61), and a = 400/21 (= 19.047)
Therefore A is the right answer.