Final answer:
The group spent 15% of their $640 budget on props, which equates to $96. By subtracting this from the total budget, we find that they spent $544 on equipment.
Step-by-step explanation:
A group of friends who were working on a student film had a budget of $640 and spent 15% of it on props. To calculate how much was spent on equipment, we need to determine the remaining portion of the budget after the props were purchased.
First, we find 15% of $640:
0.15 × $640 = $96
Then, to find the amount spent on equipment, we subtract the amount spent on props from the total budget:
$640 - $96 = $544
So, the amount spent on equipment is $544.