$$-x+1\times 2+1=1\left(3-x\right)$$
Multiply $1$ and $2$ to get $2$.$$-x+2+1=1\left(3-x\right)$$
Add $2$ and $1$ to get $3$.$$-x+3=1\left(3-x\right)$$
Use the distributive property to multiply $1$ by $3-x$.$$-x+3=3-x$$
Add $x$ to both sides.$$-x+3+x=3$$
Combine $-x$ and $x$ to get $0$.$$3=3$$
Compare $3$ and $3$.$$\text{true}$$
This is true for any $x$.$$x\in \mathrm{R}$$