To find the number of years between 1844 to 2015 you have to subtract.
Lets say that x is the # of years in between 1844 and 2015
Then we have:

After doing the subtraction using a calculator or a pencil and paper, you get that:

So 171 years have passed from 1844 to reach to 2015.
I think the probability of picking an odd number is 7/15
17% = 17/100 = 0.17
Answer: 0.17