Given: u = -6 cm (the object is 6 cm from the eye, and the direction is negative), v = 10 cm (the image is 10 cm from the eye)

Using the lens formula:  \(\frac{1}{\text{f}}\) =  \(\frac{1}{\text{v}}\) -  \(\frac{1}{\text{u}}\)

\(\frac{1}{\text{f}}\) = \(\frac{1}{10}\) +  \(\frac{1}{6}\)

\(\frac{1}{\text{f}}\) =  \(\frac{8}{\text{30}}\)

So that f = 3.75cm upon cross multiplying

Therefore, the focal length of the lens is 3.75 cm.