How to prove this number theory question?

Solve the triangle. a = 21°, c = 105°, c = 5

Rewrite the following quadratic functions in intercept or factored form. show your work. y = 5x^2 + 10x

Serena is making an experiment. for that, she needs 20 grams of a 52% solution of salt. she has two large bottles of salt water: one with 40% and the other with 70% of salt in them. how much of each must she use to make the solution she needs? i am in need of