There were 260 rabbits last year.
We know that last year was the original population as 100%. The population is now 5 times higher, as 100% x 5 is 500%.
To find the original rabbit population, we would then divide this years population of 1300 by 5, to get 1/5 aka 100% of the population. This number is 260
500/100=5
1300/5=260