Find the sum of the measures of the angles of a seven-sided polygon.

Step 1 ：Let's find the sum of the measures of the angles of a seven-sided polygon.

Step 2 ：The sum of the interior angles of a polygon can be calculated using the formula \((n-2)*180\), where n is the number of sides of the polygon.

Step 3 ：In this case, n is 7.

Step 4 ：Substitute n = 7 into the formula, we get \((7-2)*180 = 900\).

Step 5 ：Final Answer: The sum of the measures of the angles of a seven-sided polygon is \(\boxed{900}\).