A hardware store is offering 20 light bulbs at a total cost of $71.02, which includes a 6% sales tax. To prepare for a lab experiment, Brad is making a solution that uses two types of concentrations: 75 mL of 50% salt and 125 mL of 10% salt.

What is the salt concentration of the mixed solution?
Before taxes, how much did a single light bulb cost?

Sophia wrote an equation to represent the revenue of a movie theater for one day. she let x represent the number of child tickets sold and y represents the nunver of adult tickets sold. if a child ticket cost $4, an adult ticket cost $6, and the total revenue for the daybwas $420, which equation could sophia use to represent the number of chikd and adult tickets that were sold?