Question

Solve the following system of equations by linear combination: 3x+2y=7 y=x-4

Answer 1

`\left \{ {{3x+2y=7} \atop {y=x-4}} \right.`

Express
`y` from first equation:

`2y=7-3x`

`y=(7-3x)/(2)`

Then, replace
`y` in second equation with found value and solve it:

`(7-3x)/(2)=x-4`

`7-3x=2x-8`

`5x=15`

`x=15/5=3`

Now, replace
`x` in first equation with found value and solve it too:

`3*3+2y=7`

`9+2y=7`

`2y=-2`

`y=-2/2=-1`

So the result is:
`x=3` and
`y=-1`