Final answer:
The expression evaluates to 0.000007. Division involving large numbers and small decimal values should be done using scientific notation. The number of significant figures in the final answer depends on the numbers involved in the calculation.
Step-by-step explanation:
The question asks to evaluate the expression 987,654,321 + 0.000007 - 987,654,321. This calculation involves two numbers that are equal and opposite, which means they will cancel each other out when summed. The remaining term is 0.000007, which is the result of the expression.