Final answer:
The junior class needs to sell at least 50 beach towels for the fundraiser.
Step-by-step explanation:
To find the number of beach towels the junior class needs to sell, we can set up an equation based on the information given. Let x be the number of beach towels. The profit is given by the equation: Profit = Revenue - Cost. The revenue is $18 multiplied by the number of beach towels sold, and the cost is the supplies cost of $150. We want the profit to be at least $600, so we have the equation: $600 ≤ 18x - $150. Solving this inequality, we get x ≥ 50. Therefore, the junior class needs to sell at least 50 beach towels.