Question 4853
Did they really say this in that story?

Let x = Tweedledee's weight.
Let y = Tweedledum's weight. 

So, according to Tweedledum, x + 2y = 361  Rewrite as: x = 361 - 2y and substitute in the equation below: 
and according to Tweedledee, y + 2x = 362

After the substitution, we have:
 y + 2(361 - 2y) = 362  Now, solving for y:
y + 722 - 4y = 362
-3y = -360
 y = 120 lbs  This is Tweedledum's weight, which is not too bad in lbs, but if it were in stones, he would definitely be obese.

x = 361 - 2y
x = 361 - 2(120)
x = 361 - 240
x = 121 lbs  This is Tweedledee's weight and the same comment applies.

Check:

Tweedledum says, "The sum of your weight and twice mine is 361"
Since x is Tweedledee's weight, then we have:
  x + 2y = 121 + 2(120) = 121 + 240 = 361 and, contrariwise, according to Tweedledee:
y + 2x = 120 + 2(121) = 120 + 242 = 362