Question

Please someone help me
with parts C

Answer 1

Okay so for part C if you have a graphic calculator, you would press the button that say Y=, once you have that then you put 140-(30 x n) in the Y1 then you put 50 in Y2 after that hit graph wait til it graphs. Then hit 2nd trace, go to where it says intersect hit that then move the dot that appears on the graph towards when the two lines cross each other then hit ENTER three times and you'll have your answer. Sorry for the long explanation, but i hope this helps you :)

Answer 2

If the parentheses were in another place you would get a different answer.  Just like the 2 problems show.  The answers are different because of where the parentheses are placed.