The situation described can be represented by a system of equations to model the spending on pens and pencils.

Given:

• The glee club has $90 to spend.
• Each pen costs $0.75, so the total cost for $x$ pens is $0.75x$.
• Each pencil costs $0.15, so the total cost for $y$ pencils is $0.15y$.

The total cost equation is:

$0.75x + 0.15y = 90$

This equation represents the total amount spent on pens and pencils, where $x$ is the number of pens, and $y$ is the number of pencils.

Additional Details:

If you want to find out more about the relationship between the number of pens and pencils, or solve for one variable given the other, you could proceed by solving the equation. For instance, you could express $y$ in terms of $x$, or vice versa.

Would you like me to solve this equation further or help with other details?

Here are five related questions to explore further:

1. How many pens can they buy if they decide not to buy any pencils?
2. If they buy 100 pencils, how many pens can they afford?
3. What is the maximum number of pencils they can buy if they only spend on pencils?
4. How would the total spending change if each pencil now costs $0.10?
5. If the glee club buys twice as many pencils as pens, how can we model this situation?

Tip: Solving word problems often starts with translating the problem into a mathematical equation and identifying what each variable represents.