Hint: It doesn't matter how far it was to Manchester.
Answer: Blake.
On the way there Alex drove 90 miles, and on the way back drove the (total distance - 100 miles).
On the way Blake drove the (total distance - 90 miles), and on the way back drove 100 miles.
So Alex drove 90 + total - 100 = total - 10.
And Blake drove total - 90 + 100 = total + 10.
Please 
