Hi, could someone tell me how they got an answer of: x/12 for the question below:
A boat costs x dollars, and this cost is to be shared equally by a group of people. In terms of x, how many dollars less will each person contribute if there are 4 people in the group instead of 3.

Question

Hi, could someone tell me how they got an answer of:   x/12  for the question below:
A boat costs x dollars, and this cost is to be shared equally by a group of people. In terms of x, how many dollars less will each person contribute if there are 4 people in the group instead of 3.

anonymous · Answer

at first, there are 3 people
so, 
each pays x/3 dollars 
after that,  there are 4 people
so, each pays x/4 dollars
the difference between x/3 and x/4 is the amount they pay less 
=x/3-x/4=x/12

anonymous · Answer

x/3 - x/4
=4x/12  -3x/12
=(4x-3x)/12
=x/12