Hey There!

The mirror formula is given as 1/v+1/u=1/f...(i)

The position of object is 10 cm left of mirror and position of image is 25−10=15 cm right of mirror

u=−10 cm and v=15 cm substituting values in equation (i)

1/15+1/(-10)=1/f

1/f=(10-15)/150

f=−30cm

The radius of curvature is given as R=2f=−60 cm.

Hope it helped to clear your delimma.