Conrad earns a 7.5% commission on his sale of office supplies. last month, he earned $836.50 in commissions. what were his total sales for the month?

Becca wants to mix fruit juice and soda to make a punch. she can buy fruit juice for $3 a gallon and soda for $4 a gallon. if she wants to make 28 gallons of punch at a cost of $3.25 a gallon, how many gallons of fruit juice and how many gallons of soda should she buy?