How many fewer cans of food were collected by 87369 than 91761?

For each expression use a property to write an equivalent expression.

After the seventh month of a 12-month loan: the numerator is: {(n + 11) + (n + 10) + (n + 9) + (n + 8) + (n + 7) + (n + 6) + (n + 5)} = , and the denominator is: {(n) + (n + 1) + + (n + 11)} = . therefore, the fraction is numerator/denominator (to the nearest tenth) = %

[10 points, algebra 2-simplifying complex fractions]according to my answer key the restrictions are -1 and 4. but why not positive 1?