Please help with this question

Dear Student,

image distance, v = 75 cm object distance, u = - 25 cm lens formula : \frac{1}{v} - \frac{1}{u} = \frac{1}{f} \frac{1}{75} - (\frac{1}{- 25}) = \frac{1}{f} \frac{1}{f} = \frac{1}{75} + \frac{1}{25} = \frac{4}{75} f = 18.75 cm for a lens, magnification is : m = \frac{v}{u} m = \frac{75}{- 25} = - 3

Regards