Final answer:
To find QR when given RS and QS, assume the points lie on a straight line, then subtract the length of RS from the length of QS. The calculation shows that QR equals 15.1 units.
Step-by-step explanation:
To find the length of segment QR given that the length of segment RS is 39.3 units and the length of segment QS is 54.4 units, we can assume that points Q, R, and S lie on a straight line. This means that QS is the sum of QR and RS. We can set up the equation: QR + RS = QS. Plugging in the given lengths, we have QR + 39.3 = 54.4. To isolate QR, we subtract 39.3 from both sides of the equation, leaving us with QR = 54.4 - 39.3. After calculation, we find that QR = 15.1 units.