Answer:
[tex]\huge\boxed{x=18^o}[/tex]
Step-by-step explanation:
Two angles are Complementary when they add up to 90°.
Therefore
[tex]x+4x=90\qquad|\text{combine like terms}\\\\5x=90\qquad|\text{divide both sides by 5}\\\\\dfrac{5x}{5}=\dfrac{90}{5}\\\\\boxed{x=18}[/tex]
