Last years phone model had a battery that lasted 15 hours. This year the battery only last for 7.5 hours. What was the percent the battery life decreased?

In stepmber, daniel and justin opened a business. during their first three months of business, their average monthly profit was $51. if during their first month, they lost $29, and during their second month, they gained $115, what was their profit or loss for their third plzzz i will give you 299 points