Please help

In angle pqr find the measure of

Which expression do you get when you eliminate the negative exponents of 4a^2 b^216a^-3 b

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