1)

We know y's value. Let's plug it in the equation.

Divide both sides by -7.

Now we have x's value. Let's plug it in the equation to find y.

Solution,
(-2, -10)
2)

Again we have y's value. Let's plug and solve.

Now we have x's value let's solve for y.

Solution,
(-2, 0)
3)

Let's first multiply the first equation by -1

Then let's add these new equation and the second equation.

Now we have y's value let's plug it and solve for x.

Solution,
(-3, -2)