Bob bought 3 packs of model xars. he gave 4 cars to ann. bob has 11 cars left. how many model cars were in each pack

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