Answer:
If you're trying to find x or y, you cannot find the exact value since there is one equation. If there was, for example, 2 equations, [a system of equations] you could solve that. But here we only have one equation.
So, if you're trying to solve for x;
x = 7 - 3y
And if you're trying to solve for y;
y = 7/3 - x
