Complementary angles mean that they add up to 90.
Thus, we can write:
[tex]\begin{gathered} A+B=90 \\ 7x+4+4x+9=90 \end{gathered}[/tex]We can use algebra to find x:
[tex]\begin{gathered} 7x+4+4x+9=90 \\ 11x+13=90 \\ 11x=90-13 \\ 11x=77 \\ x=\frac{77}{11} \\ x=7 \end{gathered}[/tex]To find measure of the individual angles, A and B, we simple plug in 7 into x of the expressions of A and B.
Angle A:
7(7) + 4 = 53 degrees
Angle B:
4(7) + 9 = 37 degrees
