Solve the system of equations by the substitution method.?

Question

{3y = x - 30
{2x + 6y = 0

a. (15, -5)
b. (-5, 15)
c. infinite number of solutions
d. no solution

Answer 1

3y=x-30
2x+6y=0

3y+30=x

2(3y+30)+6y=0
6y+60+6y=0
12y+60=0
12y=-60
y=-5

3(-5)=x-30
-15=x-30

15=x answer is A x=15 y=-5

Answer 2

so, for the first equation you get:
x = 3y+30

substitute that into the second one to get:
2(3y+30) +6y=0

12y+60=0
y=-5

then plug y= - 5 into the first equation and you get that x = 15. choice A is correct.

Answer 3

ok for substitution, you have to substitute one equation in for another

so,set one equation equal to a singular variable
so you have

x= (3y + 30)
2x + 6y =0
Now you substitute in:
2(3y + 30) + 6y= 0
6y + 60 + 6y= 0
12y = -60
y= -5

so, your y coordinate is -5

now, substitute your y coordinate into your x= equation

x= 3(-5) +30
x= -15+30
x= 15
Your answer is A