Answer
$-0.142\;m$
Work Step by Step
The displacement of the resultant standing wave is given by
$y_R(x,t)=0.15\sin(0.79x-13t)+0.15\sin(0.79x+13t)$
Now, at $x=2.3\;m$ and $t=0.16\;s$
$y_R(2.3\;m,0.16\;s)=0.15[\sin(0.79\times2.3-13\times0.16)+\sin(0.79\times2.3+13\times0.16)]$
or, $y_R(2.3\;m,0.16\;s)\approx-0.142\;m$
Therefore, the displacement of the resultant standing wave at $x=2.3\;m$ and $t=0.16\;s$ is $-0.142\;m$
