Решите систему уравнений:

\(\displaystyle\begin{aligned}\begin{cases}7(x+y)-9(x-y)=86{\small,}\\8(x+y)+7(x-y)=81{\small.}\end{cases}\end{aligned}\)

\(\displaystyle x=\) [ ] \(\displaystyle ;\)\(\displaystyle y=\)  [ ]\(\displaystyle .\)