Okay so in this question it says to solve f(7). This means to plug in the 7 every where you see an x, so that it looks like this: 
Then you'll solve it like a normal equation.
Hope this helped! Let me know if there is anything I need to clarify or explain more in depth!
Answer:
your question is very good but I know only little bit about Mathematics this I know but my calculation is little bit mistake that's why I cannot give your answer sorry
Answer: y = 4x - 20
solution in the pic below:)!
Answer:
Statements: Reasons:
1) ∠2 and ∠4 are vertical angles given
2) limes <em>m </em>and <em>n </em>intersect at <em>P </em>definition of vertical angles
3) ∠3 and ∠4 are linear pair definition of linear pair
4) ∠2 and ∠3 are linear pair definition of linear pair
5) m∠3 + m∠4 =180 angle addition postulate
6) m∠2 + m∠3 =180 angle addition postulate
7) m∠2 + m∠3 = m∠3 + m∠4 substitution property
8) m∠2 = m∠4 subtraction property
9) ∠2 ≅ ∠4 definition of congruent(≅) angles
The sale price is 7.95 , hope this helps
