Answer:
10.2cm
Step-by-step explanation:
Perimeter is the sum of the lengths of all sides.
1st side: 9cm
2nd side: 7.8cm
Perimeter: 27cm
Perimeter = 1st + 2nd +3rd side of a triangle
27cm = 9cm +7.8cm + 3rd side
3rd side = 27cm - 9cm -7.8cm
= 10.2cm
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The measure of angle 3 from the figure is 110 degrees
<h3>Lines and angles</h3>
An angle is the intersection between two lines. From the given figure, we have the following parameters
m∠1= 40°,
m∠2= 70°.
Required
Measure of angle 3
The sum of the interior angles of the triangle is equal to the exterior
Sum of interior = <1 + <2
Sum of interior = 40 + 70
Sum of interior =110 degrees
Hence the measure of angle 3 from the figure is 110 degrees
Learn more on lines and angles here: brainly.com/question/25770607
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I think the answer is a. -3x^2-x-5