Round each number to the nearest thousand, then subtract.<br><br>&bull; 8951: hundreds digit is 9 (9 &ge; 5), round up &rarr; 9000<br>&bull; 7108: hundreds digit is 1 (1 &lt; 5), round down &rarr; 7000<br>&bull; Estimate: 9000 &minus; 7000 = 2000<br><br>Final Answer: 9000 &minus; 7000 = 2000