How to evaluate 13-5+71
i keep getting

You keep getting 79 because that's the answer silly!

I think think that you are getting the ones in the expression misunderstood for what is know as a vertical bar or pipe (|). I can see why this is tricky, but this is why you have to pay close attention in reading questions! Follow the rules of P.E.M.D.A.S. : 1. parentheses, 2. exponents, 3. and 4. multiply or divide left to right, 5. and 6. add and subtract left to right.

1. 3 - 5 + 7
2. (-2) + 7
3. = 5

Answer is either b or c