Question 1017828
two angles are complementary if their sum is 90 degrees.


if their sum is 90 degrees, then one of the angles is equal to 90 - the other angle.


for example:


30 + 60 = 90, therefore 30 and 60 are complementary.


30 = 90 - 60, therefore one of the angles (30) is equal to 90 - the other angle (60).


likewise 60 = 90 - 30.


in general:


if a + b = 90, then b = 90 - a and a = 90 - b.


your problem states to find the complementary angle of x + 3.


let y be that angle.


in order to be complmentary to x + 3, y would have to be equal to 90 - (x + 3)


y = 90 - (x + 3) becomes y = 90 - x - 3 which becomes y = 87 - x.


the complementary angle to x + 3 is equal to 87 - x.


if these angles are complementary, then their sum is 90 degrees.


x + 3 + 87 - x is equal to 90, therefore the angles are complementary.


your solution is that the angle that is complementary to x + 3 is 87 - x.