First, draw a clear diagram – your own sketch is better than any book's perfect one. Use the mirror formula, 1/f = 1/v + 1/u, remembering 'u' is negative. Here, since the object is between pole and focus, the image becomes virtual, erect, and behind the mirror, so 'v' will be positive.
I learned this by drawing light rays on our shop's floor with chalk, treating the tiles as graph paper. The diagrams in our textbook felt distant, but my own lines made the concept real.
Everyone says to just memorize the sign conventions, but for me, it clicked only when I linked it to the real, stretched shadow of my screwdriver when I held it close to a curved reflector – that’s the enlarged, virtual image you’re calculating.
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