So, if Deyonne made 25% more cookies than Cameron and Cameron made x cookies, then Deyenne made 1.25*x cookies
I don't know your options, but the possible reveniue from sales can be represented as:
Cameron's revenue: x*0.50$
Deyenne's revenue: 1.25x*50$
We can also write Deyenne's revenue as x*0.625 (I multiplied the two numbers)
Their total revenue is the sum of the two, so x*0.50+x*0.625=x*(0.50+0.625)+x*1.125
Answer
p=1.125x