(A+3) x ( -2A2+15A+6) = (-2A3+XA2+51A+18)
(3+3) x ( -2*3*2+15*3+6) = (-2*3*3+X *3*2+51*3+18)
(6) x (-2*3*2=-12 + 15*3=45 +6 = 51
(6) x (-12 +51=39)
6 x 39 =( -2*3*3= -18)+ x *3*2+(51*3+18=171)
6 x 39 -18 + x*3*2+ 171
6 x 39 =234
234 -171=63
-18 + 5x=63
X = 13.5
