Stupid Ratio Question GCSE MathsWatch
Stupid emoji correcting D to grin
You have 4 parts in the second ratio, so this can be re-expressed in any ratio provided the sum of the parts is a multiple of 4.
You also have the problem that the amount that you are dividing in the second ratio is twice the amount that you are dividing in the first ratio ... so you need to find a value for the number of parts (x) in the first ratio such that 2x is an amount which can be divided in the second ratio (i.e. it is a multiple of 4).
So ... examine the multiples of 7 and ask the question of each one whether, when you double it, you get a number which is divisible by 4.
As soon as you do, divide that number in the ratio 2:5 for your ratio A:B; and divide double that number in the ratio 3:1 for your ratio C: D, and then put them all together for your composite ratio A:B:C: D