Final answer:
By setting up a linear equation, we find the school must sell approximately 23.53 t-shirts to break even. Since the school cannot sell a fraction of a shirt, they would need to sell 24 t-shirts to reach the break-even point.
Step-by-step explanation:
To determine how many t-shirts need to be sold to break even, we need to set up a linear equation based on the information provided. We know that selling 20 shirts results in a loss of $30, and selling 100 shirts results in a profit of $650.
Let's define the number of shirts sold as 'x' and the total money gained or lost as 'y'. We have two points: (20, -30) and (100, 650). We can find the slope (m) of the line using the formula:
m = (y2 - y1) / (x2 - x1)
Substituting the values:
m = (650 - (-30)) / (100 - 20) = 680 / 80 = 8.5
This means the equation of the line can be written as:
y = 8.5x + b
Using the point (20, -30) to solve for 'b', we substitute 'x' and 'y' in the equation:
-30 = 8.5(20) + b
b = -30 - 170
b = -200
Thus, the equation of the line is:
y = 8.5x - 200
To find the break-even point where y = 0:
0 = 8.5x - 200
Solving for x:
x = 200 / 8.5
x ≈ 23.53
Since the school cannot sell a fraction of a shirt, they would need to sell 24 t-shirts to break even.