Simply. 4m - 5.
3(m-5)+m
First, use distributive property
3m-15+ m
Combine like terms
3m + m
The answer
4m - 15
64 dollars is the tax, the total cost would be $864.
Use this for percentages.
https://percentagecalculator.net/
The answer for the first question would be 3952+3952 =7903