For `M_(1)` mirror `O` act as a object , let its image is `I_(1)` then ,
`u= -15"cm" , f = -10"cm" implies (1)/(v) + (1)/(-15) = (1)/(-10) implies v = -30 "cm"`
Image `I_(1)` will act as a object for mirror `M_(2)` its distance from `M_(2)` .
`u_(1) = -(40 - 30) "cm" = -10"cm"`
so (1)/(v_(1)) + (1)/(u_(1)) = (1)/(f) implies (1)/(v_(1)) - (1)/(10) = (1)/(15) implies v_(1) = +6` "cm"
So final image `I_(2)` is formed at a distance `6` cm behind the convex mirror and is virtual.