Plug in n = 27 and we get... C = 26 + 10*n C = 26 + 10*27 C = 26 + 270 C = 296 The input n = 27 leads to the output C = 296. This means that 27 people will have the cost be $296
Do the same for n = 39 C = 26 + 10*n C = 26 + 10*39 C = 26 + 390 C = 416 The input n = 39 leads to the output C = 416. This means that 39 people will have the cost be $416
and also n = 43 as well C = 26 + 10*n C = 26 + 10*43 C = 26 + 430 C = 456 The input n = 43 leads to the output C = 456. This means that 43 people will have the cost be $456
Point P has coordinates of (4,4) and point Q has coordinates of (4,-4).
Since both points have the same x-coordinates we can subtract point Q's y-coordinate from point P's y-coordinate.
I will set the equation up and try and figure this part by yourself. I hope you learned what to do from previous questions that are very similar to this that I answered.