In the figure below, PR= 15 and QR= 9. Find PQ.
we have a line divided in two pieces,
one piece goes from P to Q , it is, PQ
the other piece goes from Q to R=QR
Also,we know
PR=15 and QR=9
now, the total line is
total line=from P to R = PR
Now, combine
total line=one piece +second piece
replace
PR=PQ+QR
put the know values into the equation
PR=15, QR=9 , then
15=PQ+9
Now, solve for PQ, substract 9 in both sides
15-9=PQ+9-9
4=PQ