Henrikh lives x blocks from his office. It takes him 1 minute per block to walk to
work and 20 seconds per block to ride his bicycle to work. If it takes him exactly
9 minutes more to walk to work than to ride his bicycle, then x equals Choose one.
A) 4  B) 7  C) 10  D) 15  E) 13.5
The best way would be...   Per km, he takes 40 secs extra if he walks   So he will take 9 mins or 9*60 secs in 9*60/40= 
<gadget id="calculator">9*60/40</gadget>
<output>27/2 = around 13.5</output>
13.5 km   ANSW13.5R:13.5
<result>E</result>
Henrikh lives x blocks from his office. It takes him 1 minute per block to walk to
work and 20 seconds per block to ride his bicycle to work. If it takes him exactly
9 minutes more to walk to work than to ride his bicycle, then x equals