68.80 because 7 is greater than 5
K is the slope of the line formed by connecting the points.
Use slope formula:

where the 2 points are the end points of the line (First and last going Left to right)

Substitute into slope formula

You can check if this is correct by going back to graph and going "up 7" and "over 2" to get from one point to the next.
Step-by-step explanation:
all work is pictured/shown
Step-by-step explanation:
these are multiplications.
you could also write
4 + 5×(p - 1)
now, we need to calculate the contents of brackets (if we can), then do the multiplications and divisions, before we can do the then remaining additions and subtractions.
if we cannot do a calculation directly (because there is a variable involved), we need to do and document the single steps for the individual parts involved.
so,
4 + 5×(p - 1) = 4 + 5×p + 5×-1 = 4 + 5p - 5 = 5p - 1
remember, a multiplication of 2 expressions is done by multiplying every term of one expression with every term of the other expression and adding the results up (by considering their individual signs, of course).