could you help me with Solve the system by substitution.

y = 2x
3x + 2y = 21
A.x = 3, y = 6
B.x = 6, y = 3
C.x = 3, y = –6
D.x = –6, y = 3

Question

could you help me with Solve the system by substitution.  

y = 2x
3x + 2y = 21
A.x = 3, y = 6
B.x = 6, y = 3
C.x = 3, y = –6
D.x = –6, y = 3

anonymous · Answer

sure thing.

Its fairly straight forward, as one of the equations gives you that y is 2x

now substitute that into the second equation to get

3x + 2(2x) = 21

this simplifies to 3x+4x=21
7x=21
7x/7=21/7
x=3

now substitute this back into your first equation
y=2x=2(3)=6

x=3 y=6

anonymous · Answer

ooooooo....thanks!

anonymous · Answer

the problem goes on to say...
Why is (6, –2) not a solution to the system of equations given?
2x-3y= 18
5x=3y=3

anonymous · Answer

is that second equation supposed to have 2 equals signs?