Distance Dhaka NM–Gabtoli is $12$ km. Sajal goes by rickshaw at $6$ km/h, rests $30$ min at Gabtoli, returns at the same speed. Kajal walks at $4$ km/h from NM. They meet at distance from NM—

Sajal reaches Gabtoli in $2$ h, rests $0.5$ h, then returns; his position from NM is $12-6(t-2.5)$, while Kajal's is $4t$. Setting these equal gives $10t=27$, so $t=2.7$ h and the meeting point is $4\times2.7=10.8$ km from NM.