Arepair service charges by the hour. the amount of money they charge is below. what equation does the repair service use to charge customers?

a. c = 40h
b. c = 30h + 70
c. c = 30h + 40
d. c = 40h + 30

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