In your first attatchment, we want to plug in 21 for t and 3 for f. The function was modeled with the tables and flowers per bowl in mind, as t and f respectivly. Doing that gives us:
[tex] 9*21+(3*3)*21+12=\\189+189+12=\\390 [/tex]
So she should have 390 flowers.
In the second attatchment, we want to plug in -2 for x, 1 for y and -2 for z. Even though they are letters, they represent some unknown value and in this case, their value is given, so:
[tex] 3*(-2)-1-3(-2)=-6-1+6=-1 [/tex]
