Lets begin with our y=mx+b, our constant(b) is 800 that she earns as a salary, our x represents the amount she sells, m then represents the commission which is 8.25% so converting that to a decimal and replacing it as m gets us y = 0.0825x+800. Replace $4500 for x and we have y=0.0825(4500)+800 solve and we get $1171.25