Answer
57.7 percent
Work Step by Step
We know that the value of gamma is given by the following fraction:
$1.52 =\frac{7(1-n)+5n}{4(1-n)}$
Where n is the fractional percent of the molecules that are monotomic. Thus, it follows:
$7-2x=7.6-3.04x$
$x=.577$
Thus, the percentage is: $\fbox{57.7 percent}$.