Answer:
1) Since AP/AB=PQ/BC, 6x/(3x+5)=x/1. Cross multiply the denominator and you will get 6x=(3x+5)*x. Simplifying it more and you are left with 3x^2-x=0
2) 3x^2-x=0. x(3x-1)=0. x=0 or x=1/3 but x=0 can't be a solution since it would make the figure absurd. x=1/3 cm
3) According to the figure PB=AB-AP=3x+5-6x=-3x+5.
PB=-3*(1/3)+5=4 cm
1 yard = 36 inches
so 720 inches = 720/36 = 20 yards.