A=5 when B=7, B=4 when C=5. (Using Ratios, 5:7 & 4:5)

Knowing the relationship between both A & C with B means that we can find the relationship between A&C themselves. (A=5, B=7)*4 ; A=20 when B=28(B=4, C=5)*7 ; C=35 when B=28Therefore, A/C = 20/35 which can be simplified to 4/7.

This question can also be done quickly by noticing that A/B * B/C = A/C (using rules of fractions)