i am stuck on part question 4 part vi

they will be equi distant after A has passed o.

so A distance from o is 5t using D=S*T we know it took 20 seconds for A to arrive at o so B will have travelled 160 metres so it will be 40m away from o its distance from o is 40-8t

so i let theses equal each other 5t=40-8t t=3.076. so add this to 20 seconds and the answer is 23.076. at the back of the book the answer is 33.333333333....

where did i go wrong?