Find x from the given series. 12, 16, 24, 36, x, 72

Let's check the differences between consecutive terms:
$$16-12=4$$

$$24-16=8$$

$$36-24=12$$

The differences are multiples of 4 ($4,8,12,\dots$). Following this arithmetic sequence of differences, the next difference must be:

$$12+4=16$$

Therefore, the value of $x$ is:

$$x=36+16=52$$

To verify, the next difference should be $16+4=20$:

$$52+20=72$$

This matches the final term.