Let, number of roses, carnations and lilies are x, y and z respectively.
So,
x + y + z = 215 ....1 )
It is given that total cost is $410.00 :
3x + y + 2z = 410 ....2 )
Also, there are 15 more lilies than roses.
z = x + 15 ....3 )
Putting value of z in eq 1 and 2 , we get :
x + y + x + 15 = 215
2x + y = 200 ....4 )
3x + y + 2( x + 15 ) = 410
5x + y = 380 ....5 )
Solving equation 4 and 5, we get :
3x = 180
x = 60
z = 60 + 15 = 75
y = 215 - 60 - 75 = 80
Therefore, number of roses, carnations and lilies are 60, 80 and 75 respectively.
Hence, this is the required solution.