I am still trying to solve for H in this equation but I am still lost

Question

MgH = (1/2)*k*(H-2-10)^2 + Mg*2

I was told to expand the square on the right, gather terms, put it in the standard quadratic form, and use the quadratic formula, but I don't know how.

Should it be Mgh=(H-12)^2+25+1685?????