Hint: It doesn't matter how far it was to Manchester.

Answer: Daniel.

On the way there Kevin drove 90 miles, and on the way back drove the (total distance - 100 miles).
On the way Daniel drove the (total distance - 90 miles), and on the way back drove 100 miles.

So Kevin drove 90 + total - 100 = total - 10.
And Daniel drove total - 90 + 100 = total + 10.

So Daniel drove 20 miles more than Kevin. QED.

Puzzle 2

Exactly how many minutes is it before seven o'clock, if 40 minutes ago it was three times as many minutes past two o'clock?

Hint: How many minutes are there between 2:00 and 7:00?

Answer: 65 minutes.

There are 300 minutes between 2:00 and 7:00 and we can ignore the "40 minutes ago" for a little while and share the remaining 260 minutes in the ratio 3:1, which is 195:65.

Which means the 5 hours between 2:00 and 7:00 are made of up 195 minutes + 40 minutes + 65 minutes.

Which means it is currently 65 minutes before 7:00. So it is now 5:55 (65 minutes before 7:00).

To double check, 40 minutes ago it was 5:15 - which is 195 minutes after 2:00, as required (as 65 x 3 = 195).

Puzzle 3

Moving up or right, what is the highest total you can make, using the mathematical signs along the way?