Hello, thank you for taking the time to post your question!
To find the Profit Function on this one you want to take
P(x) = R(x) – C(x) , where R(x) is the revenue function and C(x) is the cost function
For the information in this question that becomes
P(x) = 87x – (30x + 4074)
P(x) = 87x – 30x – 4074
P(x) = 57x – 4074, which would be the general form of the equation to model the weekly profit from the production and sale of x bicycles
I hope that helps you get moving in a better direction on this type of question! Feel free to reach out if you have any additional questions beyond that :)