In the given ratios "B" is the common term, and the values of B in both ratios are not equal.
To make them equal, find the L.C.M. of values corresponding to B i.e., 6 and 8.
L.C.M. of 6 and 8=24
Therefore, an equivalent ratio of A:B such that B=24 =5:6=5×4:6×4=20:24
Similarly, an equivalent ratio of B:C=8:9=8×3:9×3=24:27
Therefore,A:B:C=20:24:27
Let the parts be A=20x,B=24x,C=27x
=>20x+24x+27x=Rs5680
71x=Rs5680
x=Rs80
=>A=20×Rs80=Rs1600