Let us assume the common ratio to be = x
then
4x + 13x = 85
17x = 85
x = 85/17
= 5
Then
The ratio will be = 4 * 5:13 * 5
= 20:65
So the ration in which the number 85 can be separated is 20:65. i hope the procedure is clear enough for you to understand. You can always use this method for solving similar problems without taking any help from outside. Only be careful while calculating.