Answer
$x=40$
Work Step by Step
To solve the proportion, we put the product of the means equal to the product of the extremes as follows:
$$\frac{72}{96}=\frac{30}{x}\Longrightarrow x\times 72= 30\times 96\Longrightarrow x=\frac{30\times 96}{72}=40 .$$
