a plumber charges $50 to visit a house plus $40 for every hour of work. define a variable and write an expression to represent the total cos

For the second....let the number of campers = N   and the total tents = T   so we have

T =  ceiling(N/3) + 1  

The "ceiling" is defined as  ..   the least integer that is greater than or equal to (N/3)

Thus, if we had 21 campers  ...  ceiling(N/3) = ceiling(21/3) = ceiling(7) = 7

However, if we had 22 campers ... ceiling(22/3) = ceiling(7 + 1/3) = 8

The reason for using this is that we need an "extra" tent  for any "fractional"  campers

For the first one, let the total cost = C  and the time worked =T

So we have

C = 40T + 50   

{The "40T" is known as the "variable" cost and the "50" is the "fixed" cost...}