The answer is 3 cm. You just have to add the sides you know (6 and 8) and subtract that from the perimeter (18)
Alrighty, so, without the picture and the clues given I'm going to assume the image you have looks like two angles coming from the middle of a straight line. A straight line is equal to 180 degrees. 180 degrees minus 168 degrees equals 12.
Its 110 cuz it goes up 10% if it was 20% it would be 120
Given:
The slope of the line is m=0.
The line passes through the point P(-9,-3).
To find:
The equation of the line in standard form.
Solution:
Standard form of a line is:

The slope intercept form of the line is

Where, m is the slope and
is the point on the line.
It is given that the slope of the line is 3 and it passes through the point (-9,-3), so the equation of the line is



Therefore, the standard form of the given line is
.