What helped the spread of arabic language

After the rise of Islam in the Hejaz, Arab culture and language were spread outside the Arabian Peninsula through conquest, trade and intermarriages between members of the non-Arab local population and the peninsular Arabs. The Arabic language began to serve as a lingua franca in these areas and dialects were formed.

E=egg farmx=distantce between  the Berto´s trains and the meeting point. t=time where the trains meet up ⇒110 miles/h                                          ⇒85miles/h[E]X[12 miles][34 miles][ x ]
distance between Berto´s train and Eduardo´s train==12 miles+34 miles=46 miles.

S=d/t      ⇒d=S*tS=seedd=distanceT=time
Eduardo´s train;46 miles+x=t*110 miles/h  ⇒x=t*110 miles/h-46 miles  (1)Berto´s train;x=t*85 miles/h  (2)
With the equations (1) and (2) we suggest this system equations:x=t* 110 miles/h-46 milesx=t*85 miles/hwe solve this system equiations :t*110 miles/h-46 miles=t*85 miles/h110t miles/h-85t miles/h=46 miles25 t miles/h=46 milest=46 miles/25 miles/h=1,84 hour  (≈1 hour, 50 minutes, 24 seconds)
x=t*85 miles/h=156,4 miles
Solution: 1,84 hour