Someone explain this to me because i seriously don't get it.

Anyone? 15m is what percent of 60m; 3m; 30m; 1.5 km?

Solving algebraic equations 2m+3=11

I'm at a bookstore with $\$35$ in my pocket and a $20\%$-off coupon. what is the cost of the most expensive book i can buy with my money and the coupon? (assume that there are books of every possible price in the bookstore. it's a large bookstore! )