On a 100-mile hike, Mike walks 15 miles the first day, 10% of what is left the next day and 0.2 of the total the following day. What percent of the hike has Mike left to walk?

Answer: 56.5% 

Explanation: 

Since Mike walks 15 miles in the first day, 15 miles will be subtracted from 100 miles. So, Mike has 85 miles to walk after the first day. 

To compute the distance that Mike walked on the next day, we calculate 10% of what is left, which is 85 miles.

In this calculation, we convert 10% to decimal by dividing 10 by 100. 

So, 10% = 0.1. Thus,

10% of 85 miles = 0.1(85) = 8.5 miles

Then, we subtract 8.5 miles from 85 miles to get the distance left and we obtain 76.5 miles. 

Since Mike walked 0.2 of the total in the following day and the total distance is 100 miles, we just multiply 0.2 by 100, which is equal to 20 miles. 

To get the distance left for Mike to walk, we subtract 76.5 miles (which is the previous distance left for Mike) to 20 miles and we obtain 56.5 miles. 

Hence, Mike has 56.5 miles left to walk.