I don't know specifically what the sum and product of an equation is but
factor using quadratic formula
if you have an equation in ax^2+bx+c=0 then you can solve for x using

or

so input
a=1
b=7
c=2



=aprox -0.2984378812836



=aprox -6.7015621187165
The correct Anwser it is about 4 gallons because in 1 gallon tgere is 3.75 liters
Ill say 3 or 4 depends if you also want to put green peppers and salsa
V + f - e = 2
e = v + f - 2