Can anybody help me? I do not understand

9/10 divide by -3/15 as a mixed number

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 point has an coordinates of (2,0) ? a