Question

William works for a video game store. He has 30 video games at the start of the day. He sold 6 video games per day. Write the rule for the total number (N) of games as a function of the number of days (d).

Answer 1

See below.

Explanation:

It isn't clear if the problem wants to know the number of video games sold, or the number remaining.

Remaining Games

Let N be the number of video games in the store after d days. Assume none are replaced after they are sold.

N = 30 - 6d [Remaining games, N, are 30 minus the number of days, d, times 6 games/day] We need to also state 30 ≥ N ≥ 0. [No negative games are allowed. They are bad for morale].

SOLD Games

Let N be the number of games sold over n days.

N = 6d [Games sold] Here, we need to state 0 ≤ N ≤ 30. [We can't sell more games than we have, unless you are a fast runner].