If variable Z is directly proportional to X, this means that the value of X increases a certain amount when Z increases. The same will apply to decreasing of either variable.
If Z = 45, X = 15. This means Z is 3 times as much as X. X is currently 23. We can now figure out for Z.
Since Z is 3 times as much as X, multiply 23 by 3. 23 * 3 = 69
