Percentage of trans-stilbene traces in cis-stilbene H NMR
You have to focus on the $\ce{^1H}$ of the double bond. 
They are singlets because both molecules are completely symmetrical. 
As per the tables, the chemical shift of the cis isomer is $5.25+1.38-0.07=6.56$ ppm. 
On the other hand, the chemical shift of the trans isomer is
$5.25+1.38+0.36=6.99$ ppm. 

These theoretical values correspond to the peaks of 6.60 and 7.11 ppm. 
Since their integrals are of 1 and 1.1571 respectively, the proportion of trans is of:

$\frac{0.1571}{0.1571+1}100=14\%$