Yay! I'm so glad that this system of linear equations has to be solved by substitution because it is my favorite way to solve these kinds of problems. I will explain how to do this problem step by step, just like I learned in 8th grade. I hope this makes sense to you :)
Step 1: Solve for either x or y in one of the two equations.
-4x - 2y = -14
+ 4x + 4x
---------------------------
-2y = 4x - 14
------ ------ ------
-2 -2 -2
y = 2x + 7
Step 2: Plug in the solution you got for x or y into the equation you have not worked with yet. (2x + y = 7)
2x + 2x + 7 = 7 ⇒ 4x + 7 = 7
- 7 - 7
--------------------
4x = 0
----- -----
4 4
x = 0
Step 3: Plug in the solution you got in step 2 into either of the 2 equations.
2(0) + y = 7 ⇒ 0 + y = 7
- 0 - 0
----------------------
y = 7
The final solution to a systems of linear equations is written in a coordinate pair. (x,y)
In your case, the final answer would be (0, 7).