Since this is a equilateral triangle all angles are equal to each other. All angles in a triangle always add up to 180 degrees.
So you would set up your equation like so
3(7x - 3) = 180
The 3 outside the parenthesis resembles the 3 angles.
You equal the equation to 180 since all the angles in a triangle = 180
So distribute the 3
21x - 9 = 180
Add 9 to both sides
21x = 189
Divide 21 on both sides
x = 9
Well i think that is already in standard form
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2x-9y and 11x + 3y - 12y - 9x
When you have to describe a 3D shape you have to keep the following definitions in mind:
<em>1. The face of a 3D shape is a flat surface.</em>
The shape on the picture has 3 rectangular faces and 2 triangular faces, a total of 5 faces.
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<em>2. The edge is where two faces meet.</em>
For the shape on the picture, there are 3 edges, where the rectangular faces meet each other, and then three edges where the rectangular faces meet each of the triangular faces, this shape has a total of 9 edges.
<em>3. The vertex is a corner, where the edges meet.</em>
There are three vertices on each end of the shape, so it has a total of 6 vertices.
A shape that has 5 faces, 9 edges, and 6 vertices is a triangular prism.
