Answer:
His error occurred in the last step
Explanation:
He was supposed to calculate -
[tex]\frac{5}{6} - \frac{1}{9} \\or\\\frac{15}{18} - \frac{2}{18} \\[/tex]
which would equal -
[tex]\frac{13}{18} \\not\\\frac{17}{18}[/tex]
Because he added instead of subtracted.
Hope this helps!
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