The sum of two rational numbers is . if one of them is find the other.
∵ + ( A rational number) =
∴ (The required rational number) =
( ∵ LCM of 5 and 20 is 20)
What should be added to
∵ (The required number) +
∴ (The required number) =
(∵ LCM of 21 and 7 is 21 and 21 +7=3)