First, we need to set up the equation.
y = amount
x = new customer
Daniel gets 10 dollars each week. Let's think of this as a base pay, there's no variable to it.
So we start with 10.
Next, we have 3.50 dollars each week for each new customer.
So that would be 3.50 times each new customer which would become 3.50x
When you put those two together, you get y = 10 + 3.50x.