Predict the result
Simplify the fraction with four plus eight in the numerator, and five minus three in the denominator.
What must you simplify before dividing?

Set up the model
A fraction bar groups the whole numerator and the whole denominator.
First add four and eight to get twelve. Keep the complete denominator grouped.

Work the example
Five minus three is two, which is nonzero.
Now twelve divided by two equals six.

Check the result
Now use four plus six in the numerator, and eleven minus two in the denominator.
Complete both groups before dividing. Take eight seconds to think.
[Eight-second silent pause to work; the answer remains hidden.]
Four plus six is ten. Eleven minus two is nine, which is nonzero.
The result is ten ninths.

Interpret the result
Evaluate each complete group before dividing.
The denominator must be nonzero. Division by zero is undefined.
These numeric examples illustrate a grouping rule used in formulas with fraction bars.