Find the price of a $200 pair of shoes with a 6% Sale tax

What is the best way to answer questions with a x expression in the question. for example 3x + 10x=?

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

Is a square always, sometimes, or never a parallelogram