Calculate the value of X.
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Calculate the value of X.
Let's remember that the sum of angles in a triangle equals 180 degrees.
Therefore, we will use the following formula:
Let's input the known data:
We'll combine the x terms:
We'll move terms to one side and maintain the appropriate sign:
We'll divide both sides by 50:
2
Determine the size of angle ABC?
DBC = 100°
This is a fundamental property of triangles! No matter what size or shape the triangle is, the three interior angles will always sum to exactly 180 degrees.
Remember that 80 - x means you're subtracting x. When combining terms, write it as: 11x + 40x + (-x) = 50x. The negative sign stays with the x!
Check your algebra! In this problem, x should be positive since all angle expressions (11x, 40x, 80-x) need to give positive angle measures.
Yes! You could also substitute each angle expression directly: . But combining like terms first is usually faster.
Substitute back: ✓. Perfect!
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