What’s the answer? Please help!

What is the nth term rule of the linear sequence below? 27 , 25 , 23 , 21 , 19 , . .

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

Which of the following is missing in the explicit formula for the compound interest geometric sequence below?