You can put this solution on YOUR website! Here's what we know from what's given:
a = 17
a + b = 23, so b must therefore be 6.
Now plug the numbers in to the new equation:
(a + b) is the same as (17 + 6)
(a - b) is the same as (17 - 6)
Therefore the answer is
23
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11
Your teacher probably wants you to reduce it to
2 1/11 (two wholes and 1/11 of another)