16 for every 100
8 for every 50
1 for every 16
.5 for every 8
Given that initial time for jogging is,

After each week the time is increased by

This gives an arithmetic sequence.
To find n such that,

Therefore,

So,

Therefore, 9 weeks before you are up to jogging 70 minutes.
No...standard form cannot have fractions
2/3x - 1/3y = 2....multiply by common denominator of 3 to get rid of fractions
2x - y = 6 <== standard form
I'm not very sure but... here's my opinion:
I think you need at least 3 boats to ride on, because as you know, 5 is an odd number. You will have 2 friends in one boat, 2 friends in the second boat, and the one friend that is left over will go on the third boat.
Again, this is just my opinion, so I'm not sure :P
Hope I helped! :)