Let, us depicit a figure accourding to question
Here, number of people who had none of the three
=[Total-(both+all of the three)]
=[200-(10+30+10+50+10+20+60)]
=[200-190]
=10
10 candidates had none of the three. (answer)
Let, he took x hours at 60 mph.
He took (5-x) hours at 80 mph.
According to question
60x+80(5-x)=340
=60x+400-80x=340
=20x=400-340=60