Answer: The cost of 7 roses and 8 petunias is $41.
Step-by-step explanation:
Given, Bethany sells roses and petunias. The expression [tex]3r+2.5p[/tex], gives the cost (in dollars) of r roses and p petunias.
Now to find the cost of 7 roses and 8 petunias , put r= 7 and p= 8 in the above expression , we get
[tex]3(7)+2.5(8)=21+20\\\\=41[/tex]
Hence, the cost of 7 roses and 8 petunias is $41.