How are factors and multiples in solving problems?

Geometry ? i don't know how to do any of these.

Kayla and alberto are selling fruit for a school fundraiser. customers can buy small boxes of grapefruit and large boxes of grapefruit. kayla sold 3 small boxes of grapefruit and 1 large box of grapefruit for a total of $65. alberto sold 1 small box of grapefruit and 1 large box of grapefruit for a total of $55. what is the cost each of one small box of grapefruit and one large box of grapefruit?

When a valve is open 281 gallons of water go through it in one hour the number of gallons that would go through in 94 hours is