The magnification is the ratio between the size of the image [tex]h_i[/tex] and the size of the original object [tex]h_o[/tex]:
[tex]M= \frac{h_i}{h_o} [/tex]
The sign of the magnification contains another piece of information: if it's positive, then the image is upright, if it's negative, the image is inverted. In our problem, the image is inverted, so the magnification will have a negative sign, and it will be
[tex]M=(-) \frac{50 cm}{80 cm}=-0.63 [/tex]
