I need help so bad its so hard

Hello i need some with trigonometric substitutions. [tex]\int\limits^a_b {x} \, dx[/tex]

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

5. (04.07)which of the following exponential functions goes through the points (1, 12) and (2, 36)? (2 points)f(x) = 3(4)^xf(x) = 4(3)^-xf(x) = 3(4)^-xf(x) = 4(3)^x