for finding Jayant gain share= why do we multiply gain ratio ? dead partners share (2/5 ? 2/10) pls explain didnt understand the method

Here gaining share is 2:3, therefore K's share 2/10 will be taken by J&L in 2:3
Hence new ratio will be-

J = 5/10 + 2/10 x 2/5

K = 3/10 + 2/10x 3/5