PQ is a line segment 12 cm long and R is a point in its interior such that PR = 8 cm

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Given, PQ = 12 cm and PR = 8 cm
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Here, point R lies in the interior of PQ.
So, PR + QR = PQ
8+QR = 12
On subtracting 8 from both sides, we get
8 + QR-8 = 12-8 [by axiom 3]
QR=4 cm
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