Question

Use the substitution method to solve the system of equations. Choose the correct ordered pair.

2x + 3y = 29
x = 4

A. (4, 11)
B. (3, 2)
C. (4, 7)
D. (7, 4)

Answer 1

\(\Large \color{purple}{\rightarrow 8 + 3y = 29 }\)

\(\Large \color{purple}{\rightarrow 3y = 21 }\)

\(\Large \color{purple}{\rightarrow y = 7 }\)

C. (4,7)

Answer 2

In your other question I tried to explain how to do substitution method. It's pretty easy.
http://openstudy.com/study#/updates/4faa68dee4b059b524f61aee

Substitution method is that you solve for one variable in one equation (In this case solving for x in the second is given. Then you plug that into the other solution and solve for the other variable.
So then you'd have the value of y.
Then you'd plug that number back into the first equation used (so the second given solution here) and solve for the remaining variable. But you already have that.