Question

Solve the system of linear equations by substitution.
3x + y = -9
y=5x+7

Answer 1

The solution is x = -2, y = -3

Explanation:

Let's start with the equation 3x + y = -9

Substitute the y for 5x+7 seen in the second equation

Now you have 3x + (5x+7) = -9

Lets solve:

Let's add the x's

Now we have 8x + 7 = -9

Substracy seven from each side

Now we have 8x = -16

Now let's divide 8 on each side

Now we have x = -2

Now lets plug in -2 to the second equation

The second equation is y = 5x+7

When we plug in -2 we get y=5(-2)+7

We multiply

We now have y = -10+7

Add

y = -3

The solution is x = -2, y = -3