$$2y+5x-5=20+y$$
Subtract $2y$ from both sides.$$5x-5=20+y-2y$$
Combine $y$ and $-2y$ to get $-y$.$$5x-5=20-y$$
Add $5$ to both sides.$$5x=20-y+5$$
Add $20$ and $5$ to get $25$.$$5x=25-y$$
Divide both sides by $5$.$$\frac{5x}{5}=\frac{25-y}{5}$$
Dividing by $5$ undoes the multiplication by $5$.$$x=\frac{25-y}{5}$$
Divide $25-y$ by $5$.$$x=-\frac{y}{5}+5$$