1. Write the equation for the complementary angles given in the problem:
x + (x + 78) = 90
2. Simplify the equation:
2x + 78 = 90
3. Subtract 78 from both sides of the equation:
2x = 12
4. Divide both sides by 2 :
x = 6
So, the measurement of the angle is:
x = 6