Elle was asked to find the missing measure of an interior angle of a heptagon. A heptagon has angles x, 116 degrees, 115 degrees, 155 degrees, 138 degrees, 95 degrees, and 150 degrees.

Elle’s work is shown below.

Steps
Elle’s Work
Step 1
(n minus 2) 180 degrees = (7 minus 2) 180 degrees = 900 degrees
Step 2
900 minus (116 + 115 + 155 + 138 + 150)
Step 3
x = 226 degrees

Where, if at all, did Elle first make a mistake finding the measure of an interior angle?
step 1
step 2
step 3
Elle did not make a mistake.