<PRE><B>Question 1205896</B>
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There is an error in the work shown by the other tutor, which she could have found if she had checked to see if her answer satisfies the given conditions.&lt;br&gt;
Note that the error in her work was easy to make because of the awkward way she chose to set up and solve the problem.&lt;br&gt;
Informally, the difference between 15 shirts and 5 shirts is 10 shirts; the difference between being $150 short and having $250 left is $400.  That means the cost per shirt is $400/10 = $40.&lt;br&gt;
Formally....&lt;br&gt;
let x be the cost of each shirt&lt;br&gt;
The amount of money Mrs Lee had was $150 less than the cost of 15 shirts: 15x-150.&lt;br&gt;
The amount of money she had was $250 more than the cost of 5 shirts: 5x+250.&lt;br&gt;
Solve the equation that says those two expressions for the amount Mrs. Lee had are equivalent:&lt;br&gt;
15x-150 = 5x+250
10x = 400
x = 40&lt;br&gt;
ANSWER: The cost of each shirt was $40&lt;br&gt;
Presumably the formal algebraic solution was what the student was looking for.  Note, however, that the path to the answer using formal algebra is identical to the informal path.&lt;br&gt;
The student should understand the formal solution; but being able to solve the problem informally using logical reasoning is a valuable skill.&lt;br&gt;
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