Writing Homework Help

Help me study for my Mathematics class. I’m stuck and don’t understand.

1. An instrument store gives a 10% discount to all students off the original cost of an instrument. During a back to school sale an additional 15% is taken off the discounted price. Julie, a student at the local high school, purchases a flute for $306. How much did it originally cost?

1. 325
2. 375
3. 400
4. 408
5. 425