a:b = 3:4 and b:c = 2:1 => a:b:c = 3:4:2 How?

See here we have 4 values
A-3
B-4
B-2
C-1
We start by making both the b equals by multiplying them hence B-8
Now the as the B paired with A was multiplied by 2 to become 8 u do the same with A.A becomes 3*2, A becomes 6
Do same with C multiply C with 4
4*1,C becomes 4
Now we have A:B:C::6:8:4
Simplify this u get 3:4:2
Hope this helps