Answer:
I think the equation is written as 3r + 2.5p, where r is the number of roses and p is the number of petunias. To find the total cost, substitute 777 to r and 888 to p. The total cost would then be:
Total Cost = 3r + 2.5p
Total Cost = 3(777) + 2.5(888)
Total Cost = 4551
The total cost would be $4,551.