We have such system of eq
\(\left \{ {{9x-2y=19} \atop {7x=21}} \right.\)
First lets solve second eq
7x=21 /:7 divide both sides by 7
x=3
Now we can substitute it to first equation
9x-2y=19
9*3-2y=19
27-2y=19 /-27 subtract 27 both sides
-2y=-8 /:(-2) divide both sides by -2
y=4 - its the answer