Let the numerator be ‘a’ and denominator be ‘b’
Given,
Sum of a numerator and denominator of a fraction is 18.
⇒ a + b = 18 ----- (1)
Also,
If the denominator is increased by 2, the fraction reduces to 1/3.
⇒ a/(b + 2) = 1/3
⇒ 3a - b = 2 ------ (2)
Adding (1) and (2)
⇒ 4a = 20
⇒ a = 5
Thus, b = 13
Fraction is 5/13