y + -x is the same as y - x. 12/13 +(-1/13) is the same as 12/13 - 1/13. The question is now 12/13 -1/13.
12 - 1 = 11. The answer is 11/13.
12/13 + (-1/13) = 12/13 - 1/13 = 11/13
note the "+" and "-" turn it into a "-" which means you have to subtract.
The sum of 13 12 + ( − 13 1 ) is calculated by subtracting 13 1 from 13 12 , resulting in 13 11 .
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