Answer
$m=2.5$
Work Step by Step
$Given,$ $\sqrt (3m+1)=\sqrt (7m-9)$
Squaring,we get:
$3m+1=7m-9$
$3m+1+9=7m-9+9$
$3m+10-3m=7m-3m$
$4m=10$
$m=10\div4=2.5$
We need to check by putting the obtained value in the original equation :
$L.H.S=\sqrt(3X2.5+1) =\sqrt 8.5=\sqrt (7X2.5-9)=\sqrt (17.5-9)=R.H.S$
Hence,$m=2.5$ is a valid solution