Bethany sells roses and petunias. The expression 3r +2.5p gives the cost (in dollars) of r roses and p petunias What is the cost of 7 roses and 8 petunlas?

3r + 2.5p........this is saying that each rose costs $ 3 and each petunia costs $ 2.50

so if there is 7 roses and 8 petunias.....sub in 7 for r and 8 for p
3(7) + 2.5(8) = 21 + 20 = $ 41 <===