Answer
Positive $x$ direction
Work Step by Step
$y_1=(2.50\;mm)\sin[(25.1\;rad/m)x - (440\;rad/s)t]$
and $y_2 =(1.50\;mm)\sin[(25.1\;rad/m)x + (440\;rad/s)t]$
Therefore the resultant wave equation is:
$y=y_1+y_2$
or, $y=2.50\sin[25.1x - 440t]+1.50\sin[25.1x + 440t]$
or, $y=\{1.50\sin[25.1x - 440t]+1.50\sin[25.1x + 440t]\}+1.00\sin[25.1x - 440t]$
In the above resultant wave:
$\{1.50\sin[25.1x - 440t]+1.50\sin[25.1x + 440t]\}\implies$ Standing wave`
$1.00\sin[25.1x - 440t]\implies$ Traveling wave`
Therefore, the traveling wave moves in the positive $x$ direction
