μ = –15 cm; f = +10 cm ; v = ?

Using lens formula

1/f = 1/v - 1/u

1/v = 1/f + 1/u

1/v = 1/10 + (1/(-15))

1/v = 5/150

v = +30 cm

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Magnification

m = v / μ

m = + (30/(-15))

m = -2

The image formed will be real and inverted and twice the size of the object.