Question

(12-x)²...................

Answer 1

(12-x)*(12-x)=(12*12) + (12*-x) +(-x*12)+(-x*-x)=
$x^{2} -12x-12x+12*12= x^{2} -24x+144$

Answer 2

(12-x)^2 = 12^2 -2.12.x + x^2
               =  144 - 24x + x^2