by 5 is divisible every number which ends with 5 or 0. by 3 is deviseble every number which has a quer sum devisible by 3 and for 8 every number which is devisible whit 2 for 3 times in a row for example 16:2=8:2=4:2=2
Now if you want a number devisible by all em. You need to know 3 and 5 are primes, so the number must have 15 as a factor, and becouse 15 is made of prime factors, it also need to have 8 as factor
so it can practicly be any number which has
15*8=120 as a factor
hope it helps
example
120, 240 , 360.....