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In a triangle, the sum of the measures of the first two angles is 12 less than the measure of the third angle. In addition, the measure of the first angle is twice as big as the measure of the second angle. Create and solve a system of linear equations to represent this situation. Then select the true statement.

А. The solution to this system is nonviable because it results in a negative angle measure.
B. The solution to this system is nonviable because it results in too large of an angle measure.
C. The solution to this system is viable.
D. The solution to this system is nonviable because it results in fractical values for the angle measures.

Respuesta :

the sum of the internal angles of a triangle are equal to 180 degrees.

once i remembered that the problem became a lot easier.

let a, b, and c be the angles of the triangle.

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let a = 2*b

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let c = a+b-12

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the above two statements are given.

since the sum of the internal angles of a triangle are equal to 180, then we have a third equation to work with which is

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a + b + c = 180

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we now have 3 equations for 3 unknowns and we should be able to solve for each of the unknowns.

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it looks like the easiest thing is to solve for b. once we find b, the rest should fall into place very nicely.

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since a = 2*b, we can substitute 2*b for a in the equation a + b + c = 180.

that equation then becomes 2*b + b + c = 180 which becomes 3*b + c = 180.

looking at the equation c = a + b - 12, we solve for b as follows:

since we know that a = 2 * b, we can substitute 2*b for a and the equation becomes c = 2*b + b - 12 which becomes c = 3*b - 12.

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the equation we are working with is 3*b + c = 180 which originally started as a + b + c = 180.

we can substitute 3*b - 12 for c and the equation becomes

3*b + 3*b - 12 = 180 which becomes 6*b = 192 after adding 12 to both sides and combining like terms.

dividing both sides of the equation by 6 and we get b = 32 degrees.

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we have b = 32 degrees.

we have a = 2 * b so a = 64 degrees.

we have c = a + b - 12 which becomes c = 32 + 64 - 12 which becomes c = 96 - 12 which becomes c = 84 degrees.

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substituting in the equation a + b + c = 180, we get 32 + 64 + 84 = 180 which becomes 96 + 84 = 180 which becomes 180 = 180.

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answer is:

a

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