Respuesta :

Since a complementary angle is two angles that equal 90 degrees the compliment of angle B would be 30 degrees since 60+30 = 90.
Solutions 

Complementary angle are two angles whose sum is 90°. We know that 
Angle b measures 60°. 

60
° + (X) = 90° 

90
° - 60° = (X) 

90
° - 60° = 30° 

(X) = 30
° 

30
° complementary to Angle B