Bob is hiking down a 60-mile country trail. He could hike at 10 mph for the first two hours and then go the rest of the way at 30 mph or he could just go the whole way at 20 mph. How long would each of these options take? Which option is the faster?

Time taken for option one: 10mph (2hours) + 30mph (rest of the way) 
Time taken for option two: 20mph (3 hours) 

Calculate the time taken by option one, 30 mph: 
60=20+30x 
40/30=x 
4/3 =x 
1+1/3=x 

It would take (option 1): 2+1+1/3= 3 1/3 hours to complete 
It would take (option 2): 3 hours

Therefore, option two is faster.

Hope I helped :)