A man covers a certain distance at a certain speed. Had he moved 6 km / h faster, he would have taken 4 hours less. If he had moved 8 km / h slower, he would have taken 10 hours more. How much time (in hours) will he take to cover the same distance with his usual speed?
1
20
2
12
3
18
4
More than one of the above
5
None of the above