7n + the squareroot of n =18
It might help for you to let x^2=n, then
7x^2+x-18=0
which can be solved by use of the quadratic equation, then when you have x, square it, and you have n.
7x^2+x-18=0
which can be solved by use of the quadratic equation, then when you have x, square it, and you have n.