In the given diagram, if AP = 15 cm, AQ = 24 cm and PB + QC = 26 cm, find QC – PB, given PQ || BC.

Answer:
QC - PB = 6
Step-by-step explanation:
Given PQ is parallel to BC then it divides the sides proportionally, that is
[tex]\frac{AP}{AQ}[/tex] = [tex]\frac{PB}{QC}[/tex] = [tex]\frac{15}{24}[/tex] = [tex]\frac{5}{8}[/tex] , then
[tex]\frac{PB}{QC}[/tex] = [tex]\frac{5}{8}[/tex] ( cross- multiply )
8PB = 5QC → *
Given PB + QC = 26 , then
PB = 26 - QC
Substitute into *
8(26 - QC) = 5QC ← distribute left side
208 - 8QC = 5QC ( subtract 5QC from both sides )
208 - 13QC = 0 ( subtract 208 from both sides )
- 13QC = - 208 ( divide both sides by - 13 )
QC = 16
Thus PB = 26 - QC = 26 - 16 = 10
QC - PB = 16 - 10 = 6