if <a and < b are complementary angles and m < a=4m < b which are the measures of < a and < b
Let's just forget the confusing < "angle" signs and "m" which I assume means "measure", and let a and b be angles in degrees.
a + b = 90 because they are complementary
a = 4 b
Therefore 5 b = 90, and b = 18.
Solve for a with either equation.