print 1 to n and print multiple of 3 replace rest with x code example

Example: develop an algorithm that prints 2 numbers so that one is a multiple of the other

You can simply use % Modulus operator to check divisibility.
For example: n % 2 == 0 means n is exactly divisible by 2 and n % 2 != 0 means n is not exactly divisible by 2.