Answer:
the missing side is 29 so point D or bubble 2
Explanation:
use the formula a^2 + b^2 = c^2
20^2 + 21^2 = ?^2 find the answer for the squared values
400 + 441 = ?^2 Add the values
841 = ?^2 in order to get rid of the power square root on both sides
_/- 841 = ? solve
29 = ?