Correct Answer - `50cm` right of `B`
For first reaction:
`(1.5)/(v_(1)) - (1)/(-10) = (1.5-1)/(10) rARr v_(1) = -30cm`
For secound refractions
`u = -(30+20) = -50cm`
`:. (1)/(v_(2)) - (1.5)/(-50) = (1-1.5)/(-10)`
`rArr v_(2) = 50cm`
Hence, final image is formed `50cm` right of `B`.