How to do algebraic expression

The mean temperature for the first 4 days in january was 7°c. the mean temperature for the first 5 days in january was 5°c. what was the temperature on the 5th day?

The distributive property allows you to say that 3(x − 1) = 3x −

Rose bought a new hat when she was on vacation. the following formula describes the percent sales tax rose paid b=t-c/c