HELP ME PLZ NOW IM GETTING desperate

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

Afrequency table of grades has five classes (a, b, c, d, f) with frequencies of 3, 13, 14, 5, and 3 respectively. using percentages, what are the relative frequencies of the five classes?

Solve each quadratic equation by factoring and using the zero product property. x^2 + 18x = 9x