Question

(1-x)(2-x)=(x+3)(x-4)

Answer 1

 

$1*2-2*x-x*1+(-x)*(-x)=x*x+3*x-4*x-4*3; 2-3x+x^2=x^2-x-12; 2+12=-x+3x; 14=2x; x=7$

 

Answer 2

2-x-2x+x^2=x^2-4x+3x-12

x^2+2-3x=x^2-x-12

2-3x=-x-12

2+12=-x+3x

14=2x

7=x