I have 3 questions with my answers and would like you to check them. If they're wrong, then please provide and explanation to how to do them. Thank you tutors.

Write each sentence as an equation.
1. Eight less than 1/3 a number n is -13.
My answer: 1/3-8n = -13

2. A number f multiplied by -12.3 is -73.8.
My answer: -12.3f = -73.8

Write an equation. Then, solve.
3. Fifteen tickets cost $193.75. What is the average cost of each ticket?
My answer: 15x = 193.75 $12.92 per ticket

I have one more question/problem that I don't know how to write an equation for. If you could provide me an explanation for me then that would be much appreciated by me.

Write an equation. Then, solve.
1. A student walks 1/4 mile from her home to the store on her way to a friend's house. If the store is 1/3 of the way to her friend's house, how far is her friend's house from her home?