Answer:
37
Step-by-step explanation:
Let's use the rule GEMDAS (Grouping, Exponents, Multiply, Divide, Add, Subtract) from left to right. Therefore, we will simplify the equation in the parentheses. 
. -(-7) creates a double negative, deeming the 7 positive, because when there is two negatives the number will turn into a positive. 
= 49, -3 x 4= -12. Therefore the final form of the equation will be 49 - 12 = 37.
Let me know if there are mistakes.
If we identify the lines by ...
1. y = -0.5x -3
2. y = -3.5x -15
3. y = 5x +19
4. y = 1.25x +4
Then the matches are ...
BC - 2
DE - 1
FG - none
HI - 4
JK - none
LM - 3
_____
Whenever there is a lot of repetitive math to do, I usually find it easier to let a calculator or spreadsheet do it. Here, the graphing calculator is computing the slope between the points. The slopes of parallel lines are the same.
"The sum of a number and 7"
Sum implies addition.
We would write this part as <em>n + 7</em>.
Then we would write the "9 times" part in like this:
<em>9 </em><em>·</em><em> </em><em>(n + 7)</em><em>
</em>We can't write just 9 · n + 7 without the parentheses, because then we would be multiplying just 9 and n instead of 9 and the sum of n and 7. (order of operations says we must do multiplication first)
