Answer: First, improper fractions are those in which the denominator is bigger than the numerator.
Now, our number is 17.099999..... let's call it X.
if we multiply X by 100, we get 100*X= 1709.999999.....
if we now do 10*X = 170.999999....
Is easy to see that subtracting those two numbers, the repeating decimals go away, so, 100*X - 10*X= 90*X = 1709.9999... - 170.999... = 1539
so if 90*X = 1539, then X = 1539/90 which is your improper fraction.