Two angles are complementary when their sum is equal to 90°.
So, ( 2x + 39 ) + ( 7x - 21 ) = 90°
9x + 18° = 90°
x = 8°
Putting value of x in the angles given :
( 2x + 39 )° = 2(8°) + 39° = 55°.
( 7x - 21 )° = 7(8°) - 21° = 35°.
Therefore, the angles are 55° and 35°.
Hence, this is the required solution.