$$ (1)\space 4v+9w =-19\qquad |\cdot \frac{7}{4}\\ (2)\space \underline{7v-2w =20}\\ (1)'\space 7v+\frac{63}{4}w =-\frac{133}{4}\\ (2)\space\underline{7v-2w =20}\\ (1)'1-(2)⇒\\ \frac{63}{4}w+2w=-\frac{133}{4}-20\\\frac{71}{4}w=-\frac{133}{4}-\frac{80}{4}=-\frac{213}{4}\\ \frac{71}{4}w=-\frac{213}{4}\qquad |\cdot 4\\71w=-213\qquad |:71\\w=-3\\in(2)\\7v-(-6)=20\\7v+6=20\\7v=14\\v=2$$
