So this is what my first answer was supposed to be.
Profit = revenue - cost
So if we replace the words with your equations you’ll get this
Profit = 2x -(0.17x + 75)
To make that make since I’ll explain again.
$2 x # of cupcakes sold -($0.17 cost of each cupcake made x # of cupcakes sold + $75 for additional one time charge)