Question 1065159
Let A be the first container (the one with more water)
Let B be the second container
A + B = 35
A - 7 = 4(B+7)
A-7 = 4B+28
A = 4B+35
Substitute that value into the first equation.
A + B = 35
(4B+35) + B = 35
5B + 35 = 35
5B = 0
B = 0
Tricky question!  There was nothing in B.  Which means A had 35 quarts.  When A transferred 7 of its 35, it now had 28.  B now had 7.  7 is 4 times 28.
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ETA: Thank you for your clarification.  You are correct (if ill-mannered.)  I have written to the student to let him know.