7.131. $\left\{\begin{array}{l}\log _{4} x+\log _{4} y=1+\log _{4} 9, \\ x+y-20=0 .\end{array}\right.$
Solution.

Domain of Definition: $\left\{\begin{array}{l}x>0, \\ y>0 .\end{array}\right.$

We have $\left\{\begin{array}{l}x y=36, \\ x+y=20,\end{array}\right.$ from which $\left\{\begin{array}{l}x_{1}=2, \\ y_{1}=18 ;\end{array}\left\{\begin{array}{l}x_{2}=18, \\ y_{2}=2 .\end{array}\right.\right.$

Answer: $\quad(2 ; 18),(18 ; 2)$