Factor all three
15.6 = .2 * 78 = .2*2*39 = .2*2*3*13
14.4 = .2 * 72 = .2*2*36 = .2*2*2*18 = .2*2*2*3*6 = .2*2*2*3*2*3
6 = 2*3
6 is common in all three numbers, divide it out of all three
15.6/6 = .2*13 = 2.6
14.4/6 = .2*2*2*3 = 2.4
6/6 = 1
ratio is 2.6 : 2.4 : 1