Can someone of you me with this math problem ?

Which of the following system of equation is not equal to the system of equations is not equal to the system of equations shown below

Given a: b and b: c, find a: b: c. write the ratio in simplest form. a: b=6: 10 and b: c=21: 33

1yd 1 ft = 1 1/12 1 1/3 1 1/2 1 1/6