CAN SOMEONE PLZZZ EXPLAIN MEAN, MEDIAN, RANGE, AND VARIABILITY;I DON'T UNDERSTAND

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

Jonathas wants to get a cell phone. the phone costs $59 and the plan costs $39 per month.

Alarge cheese pizza costs $18. each topping you add on costs $1.50. how much would it cost to get a large cheese pizza with cc toppings added? write your answer as an expression