#### Answer

Two angles are complementary angles if and only if they have measures with a sum of 90.

#### Work Step by Step

Reversing a statement is similar to writing the converse of a conditional in that you switch the phrases at the start and end of the statement.
Two angles with measures that have a sum of 90 are complementary angles.
The given statement is reversible, because the reversed statement is true.
To write a biconditional, separate the starting and ending phrases with "if and only if".