Just e and f? Explain it too please

(Image: Dividing fractions)

What is the missing constant term in the perfect square that starts with x^2 -20x

How much dextrose 70% must be mixed with dextrose 5% to prepare 1,000 ml of dextrose 20%?

Kayla has a $500 budget for the school party.she paid $150 for the decorations.food will cost $5.50 per student. what inequality represents the number of students,s, that can attend the party?