3 and 6 are both Int, and dividing one Int by another gives an Int: that’s why you get back 0. To get a non-integer value you need to get the result of the division to be a non-integer value. One way to do this is convert the Int to something else before dividing it, e.g.:
val num = 3.toDouble() / 6
num will now be a Double with a value of 0.5, which you can format as a string as you wish.