Can anybody tell me logic behind this

GRE Quant Problem Solving
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Possible value for a and c = 2 hence, we substitute it in our given Qty A and B

\frac{a}{b+1}= \frac{c}{d+2}\\ \frac{2}{b+1}=\frac{2}{d+2}

Now, it’s given that 0<b<d thus, we shouldn’t sub. 3 as a potential value for b and d but let’s do it anyways

\frac{2}{3+1}= \frac{2}{3+2} \text{ or } \frac{2}{4} = \frac{2}{5}

Here, Qty A > QtyB. Now, as we’re given 0<b<d let’s make d=3.1 and b will remain 3 and a=c= 2

\frac{2}{4} = \frac{2}{5.1}

Here, also we get Qty A > QtyB and as we keep increasing the value of d our Qty B will get smaller and smaller hence, Qty A > QtyB