Lizzy: June has $500 for buying school supplies for the new school year. She buys four maths books at $20 each, six more science books than maths books at $10 each, and twice as many art books as maths books at $20 each. If she also bought music books, how much money did she spend on music books?.
Me: Hmmm, let me think. I think this is the detailed solution:
The total cost of maths books is 4 * 20 = $80$. She bought six more science books than maths books which totals 6 + 4 = 10 books. If each science book cost her $10 she spent 10 * 10 = $100 on science books. There were twice as many art books as maths books which total 2 * 4 = 8. The total cost for art books is 8 * 20 = $160. The total amount that she used for maths, science, and art books is 160 + 100 + 80 = $340. The amount she spent on music books is 500 - 340 = $160. Final answer: 160.