Question 1065165
Let N be north-south
Let W be east-west
We know from the question that N =.75W.  Also, that N + W = 1400.
Substitute.
N + W = 1400
.75W + W = 1400
1.75W = 1400
Divide each side by 1.75
W = 800
If 800 cars went east/west, then 1400-800=600 cars went north/south.
Does 600 equal 3/4 of 800?  Yes.  Therefore, the answer is correct.