A fort had provisions for 300 men for 90 days. After 20 days, 50 men left the fort. How long would the food last at the same rate?

Can someone check if i did this correct. it’s number 4 if you’re wondering.

Which questions would most a reader identify the author's purpose for writing? check all that apply. what type of text is this? what type of reviews did the book receive? how many copies of the book have been sold? what is the central idea? how does this text make one feel?

Ineed here’s a picture of the question