Which equation shows how to find the difference 6/7 - 1/2 ?
a. 6/7 - 1/2 = 12/14 - 7/14 = 5/14
b. 6/7 - 1/2 = 6/7 - 5/7 = 1/7
c. 6/7 - 1/2 = 6/7 - 6/12 = 1/19
d. 6/7 - 1/2 = 1/2 - 1/2 =0