There are 260 economic and 100 business. there are 360 TOTAL seats, and the ratio of eco to business is 13:5, so lets suppose there are 13x eco and 5x business. 13x+5x=360 18x=360 x=20 so 13x=260 and 5x=100 there are 260 eco seats and 100 business seats.
The first thing you want to do is add 13+5 which gives you 18. SO then you see how many times 18 goes into 360. Which gives you 20. So then you multiply 20 by 5 (because there are 5 business seats for every 13 and 18 went into 360 20 times, which gives you 100 business seats. Then you subtract 100 from 360 to see how many economy seats are left which gives you 260 economy seats. So there are 100 business seats and 260 economy seats.
