A certain lens focuses light from an object 2.75 m away as an image 48.3 cm on the other side of the lens.?

Question

What type of lens is it and what is it focal length?

Answer 1

1/object + 1/image = 1/focus

focus = 1/(1/object + 1/image)

This is characteristic of a converging lens.

Answer 2

you have

1/p' = 1/p +1/f

p' distance of the image to the lens
p distance of the object to the lens
f focal length

here p' = 0.483m p =-2.75m

so
1/f = 1/0.483-1/(-2.75) = 1/0.483+1/2.75 =0.364+2.071=2.424

f= 0.411m positive lens (convex)