Final answer:
To reach the point where the cost of the carnations is equal to the revenue from selling them, the school band needs to sell at least 8 carnations.
Step-by-step explanation:
To find when the cost of the carnations will be equal to the revenue from selling them, we need to set up an equation. Let x be the number of carnations sold. The cost of buying x carnations is given by 0.50x + 18, and the revenue from selling x carnations is given by 3x. So, we set up the equation:
0.50x + 18 = 3x
Solving for x, we get:
18 = 2.50x
x = 18 / 2.50
x = 7.2
Since we can't sell a fraction of a carnation, we round up to the nearest whole number. Therefore, the school band needs to sell at least 8 carnations to reach the point where the cost of the carnations is equal to the revenue from selling them.