中二百分比

Let X be the orginal weight of the cat,
and Y be the orginal weight of the dog.
Given:
If the weight of the cat is increased by 20% while that of the dog is decreased by 10%, their weights will be the same. (*Note: the cat originally weighs less than the dog.)
i.e. (1+20%)X = (1-10%)Y
Question:
What percentage of dog's original weight is cat's original weight?
i.e. X/Y= ?%
Solution:
From given above,
(1+20%)X = (1-10%)Y
X/Y = (90%/120%)(100%)
= (3/4)(100%)
= 75%
Therefore the cat's original weight is 75% of dog's weight. (*This agrees with the given condition. 133% in Answer 001 does not seem correct.)

First, the following is my thinking processes,
that means the writing method may be wrong.

Let the original weight of cat be C kg
the original weight of dog be D kg
Now their weights are 1.2C & 0.9D
their weights is the same!
so,
1.2C = 0.9D
C / D = 1.2 / 0.9
C / D * 100%
=1.2 / 0.9 * 100%
=133% (3 sig.fig.)

4:3 ?