Caroline places five poles a, b,c, d,and e in order along a straight line. the distance poles a and d is 1 yard. the distance between poles a andb. poles a and b are 1/5 yard apart. the distance between d and e is 7/10 yard. how far apart are poles b and e?

We have

A              B                C                  D                  E 
 
                    1 yard 
  
 1/5 yard                                            
                                                              7/10 yard
The distance poles B and D= (1-1/5)=4/5 yard

The distance poles B and E= BD+DE=4/5+7/10=(8+7)/10=15/10=3/2 yard

the answer is 3/2 yard (distance poles B and E)