Question 303325
Complementary angles add to 90 degrees. So if 'x' and 'y' are complements of each other, then {{{x+y=90}}}. If we let {{{x=21}}}, then we get {{{21+y=90}}}. From here, subtract 21 from both sides to get {{{y=69}}}. So the complement of 21 degrees is 69 degrees.