To determine whether the combination of lenses works as a converging or diverging lens and to find the focal length of the combination, we can use the lensmaker's formula:

1/f_combination = 1/f_convex + 1/f_concave

Given that the focal length of the convex lens (f_convex) is +30 cm (since it is a converging lens) and the focal length of the concave lens (f_concave) is -20 cm (since it is a diverging lens), we can plug these values into the formula:

1/f_combination = 1/30 + 1/(-20)

Now, let's calculate it:

1/f_combination = (1/30) - (1/20) = (2/60) - (3/60) = -1/60

Now, take the reciprocal of both sides to find the focal length of the combination:

f_combination = -60 cm

The negative focal length indicates that the combination of lenses works as a diverging lens. So, the correct answer is: Diverging, 60 cm