A math club is having a bake sale as a fundraiser to raise money for an upcoming trip. They sell $54$ cookies at three for $\$1$, and $20$ cupcakes at $\$2$ each, and $35$ brownies at $\$1$ each. If it cost the math club $\$15$ to bake these items, what was their profit?
To find the profit, I need to subtract the cost from the revenue. The revenue is the total amount of money they collected from selling the items. To find the revenue from the cookies, I need to divide the number of cookies by three, since they sold three for $\$1$. That gives me $\frac{54}{3}=18$ dollars. The revenue from the cupcakes is easy, since they sold each one for $\$2$. That gives me $20\times 2=40$ dollars. The revenue from the brownies is also easy, since they sold each one for $\$1$. That gives me $35$ dollars. The total revenue is the sum of these three amounts: $18+40+35=93$ dollars. The cost is given as $\$15$, so the profit is $93-15=78$ dollars. 