Answer :
f = 20cm, u = -28cm
[tex] \frac{1}{v} - \frac{1}{u} = \frac{1}{f} \\ \\ \frac{1}{v} = \frac{1}{u} + \frac{1}{f} =\frac{1}{-28} + \frac{1}{20} \\ \\ \frac{1}{v}= \frac{-5+7}{140} = \frac{2}{140} \\ \\ v=\frac{140}{2}=70cm[/tex]
[tex]m= \frac{v}{u} = \frac{70}{-28} =-2.5[/tex]
The image is formed at 70cm to the right side of lens. It is real, inverted and magnified.
[tex] \frac{1}{v} - \frac{1}{u} = \frac{1}{f} \\ \\ \frac{1}{v} = \frac{1}{u} + \frac{1}{f} =\frac{1}{-28} + \frac{1}{20} \\ \\ \frac{1}{v}= \frac{-5+7}{140} = \frac{2}{140} \\ \\ v=\frac{140}{2}=70cm[/tex]
[tex]m= \frac{v}{u} = \frac{70}{-28} =-2.5[/tex]
The image is formed at 70cm to the right side of lens. It is real, inverted and magnified.