Linear Equation from Party Cost Graph: Fixed Cost and Per-Guest Rate

Published on November 9, 2026

Word-Problem

Write a linear equation modeling total party cost from a graph showing a fixed room rental fee and a per-guest charge. Read the y-intercept as the fixed cost and compute the slope from two points on the line to get C = 12x + 40.

Question

Answer

Step 1: Find the fixed cost (y-intercept).
The line crosses the vertical axis at $40, so the fixed cost to rent the room is $40.
Step 2: Find the cost per guest (slope).
The line passes through . Using the rate of change between and :
Step 3: Write the linear model.
Let be the number of guests and the total cost:
Final answer: , where the fixed cost is $40 and each guest adds $12.