To reduce fraction we have to divide numerator and denominator by the same number. We can repeat operation few times.
Lets do this
\(\frac{35}{100}= \frac{35:5}{100:5}= \frac{7}{20}\) - its the most reduced form. We cant divide 7 and 20 by the same number to not obtain number with coma. (because 7 is prime number so can be divided only by 1 and by 7)