PLZ HELP ME HELP A DUMB CHILD OUT

If you are just building your payment history, how many points from a perfect score will you possibly miss?

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

Given sin28.4=.4756, cos28.4=.8796, and tan28.4=.5407 find the cos of 61.6