Applicare la formula: $ax+by$$=\left(\frac{a}{mcd\left(a,b\right)}x+\frac{b}{mcd\left(a,b\right)}y\right)mcd\left(a,b\right)$, dove $a=-2$, $b=-\frac{1}{2}$, $ax+by=-2x-0.5z+4$, $ax=-2x$, $by=-0.5z$ e $y=z$

Applicare la formula: $x\left(a+b\right)$$=xa+xb$, dove $a=x$, $b=\frac{1}{4}z$, $x=-1$ e $a+b=x+\frac{1}{4}z$