Ok so a compass, is a technical drawing instrument that can be used for inscribing circles or arcs. Compasses can be used for drafting, navigation and graphing.
The function

is a parabola concave up, whose solutions are

from here, you can use the quadratic formula

to find that the solutions of the parabola are 
So, the parabola is positive if
(which wouldn't make sense in our case) or 
So, if Tanya caters 25 meals she breaks even, and starting with the 26th meal she will begin to profit.
Chocolate Chip: $20
Cherry Vanilla:$18.29