Question

3x + y = -1
2x + 3y = 18

Answer 1

Answer:
`x=-3\\y=8`

Explanation:

`3x+y=-1\\2x+3y=18`

Multiply by -3 the upper equation to make y equal in value but with opposite signs.

`(-3)(3x+y=-1)\\-9x-3y=3`

Now add equation 1 and 2.

`-9x-3y=3\\2x+3y=18`

--------------------------

`-7x=21`

Solve for x;

To isolate x, divide by -7

`(-7x)/(-7)=(21)/(-7)`

`x=-3`

Now use one of the equations above and replace the value of x.

`3x+y=-1\\3(-3)+y=-1\\-9+y=-1\\y=-1+9\\y=8`

To prove if it's correct, take either equation and replace both x and y values, if the results are equal to each other, it is correct.

`2x+3y=18\\2(-3)+3(8)=18\\-6+24=18\\18=18`