1ya,aditya's right.but thre cn be another solution also.
for solution,take two sets with difference d and d1 respectively.
u'll get one term common in both i.e. 5.then use the final condition to get the common differences.u'll get d=2,-16 and d1=1,-17.
then,two sets will be (4,5,6 and 3,5,7) and (21,5,-11 and 22,5,-12)
