What should you substitute for y in the bottom equation to solve the system by the substitution method? A. y=3x+15

B. y =-x-5

C. y=x+5

D. y=-3-15

y= -x-5

Step 1: Determine which equation to change

Since we will be using the substitution method, we will need to substitute y from the bottom equation with information from the top equation. This will be the equation we change.

Step 2: Change the equation

Let’s rewrite the equation we will be working with.

3x+3y= -15

Our goal will be to get y alone on the left side. To start, let’s subtract 3x from both sides, leaving only 3y on the left side.

3x+3y= -15
3y= -3x-15

Now we need to get y completely alone by eliminating the coefficient of 3. Let’s do this by dividing each term by 3.

3y= -3x-15
y= -x-5

This is your answer. Hope this helps! Comment below for more questions.