<PRE><B>Question 408718</B>
A wooden box weighs 22kg when it is half full of apples and weighs 15kg when it is one-third full of apples.
 What is the weight of the box empty?
;
let b = weight of empty box
let a = weight of just the apples when box is full
:
b + {{{1/2}}}a = 22
b + {{{1/3}}}a = 15
:
multiply the 1st equation by 6, multiply the 2nd equation by 9, 
Subtract the 1st from the 2nd equation
9b + 3a = 135
6b + 3a = 132
-----------------subtraction eliminates a, find b
3b = 3
b = 1 kg is the weight of the box

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