SPARK in Dallas requires a school to send 2 adults for every 20 students who visit for a field trip. If a school send 13 adults, how many students can go on the trip

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