Respuesta :
The answer is B
let me show my answer
-3x+y=7;9x+21=3y
Solve -3x+y=7 for y
Add 3x to both sides
-3x+y+3x=7+3x
y=3x+7
Substitute 3x+7 for y in 9x+21 =3y
9x+21=3y
9x+21=3(3x+7)
Simplify both sides of the equation
9x+21=9x+21
Add -9x to both sides
9x+21+-9x=9x+21+-9x
21=21
Add -21 to both sides
21+-21=21+-21
0=0
Answer : B , Infinitely many solutions
I hope that's help !
Have a great day !
Answer:the answer is There are an infinite number of solutions.
Step-by-step explanation:took the test and got it right