SAT Question 4f89e4d4: Linear Functions answer and explanation with Desmos solution

It's given that a student council group uses the function $p\left(x\right)=5x-220$ to determine their profit $p\left(x\right)$, in dollars, for selling $x$ school posters. Substituting $900$ for $p\left(x\right)$ in the given function yields $900=5x-220$. Adding $220$ to each side of this equation yields $1,120=5x$. Dividing each side of this equation by $5$ yields $224=x$. Therefore, in order to earn a profit of $$900$, they must sell $224$ school posters.