Answer:
15 cm
Explanation:
using the thin lens formula for convex lens
[tex]\frac{1}{f} = \frac{1}{p} + \frac{1}{q}\\ \\where f = focal length \\ p = object distance \\ q = image distance\\[/tex]
so,
[tex]\frac{1}{q} = \frac{1}{f} - \frac{1}{p} \\\\\frac{1}{q} = \frac{1}{10} - \frac{1}{30} \\\frac{1}{q} = \frac{2}{30}\\\frac{1}{q} = \frac{1}{15cm}[/tex]
so,
q = 15 cm
