When setting up an inequality, using the key words from the problem will help. The word 'difference' would indicate subtraction and 'less than' would be the '<' inequality sign. Since the expression is 'the difference of a number and -6', we write:
n - (-6) < 9
Whenever we subtract a negative number, we change both signs to positive:
n + 6 < 9
Using inverse operations to solve: n + 6 - 6 < 9 - 6
