The angles of a triangle are 128º, 5x + 10º, and 9xº.

What is the value of x?

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The three angles of all triangles will equal to 180 degrees.

128 + 5x + 10 + 9x = 180

Add up all the like terms.

128 + 5x + 10 + 9x = 180

138 + 14x = 180

Subtract each side by 138.

138 + 14x - 138 = 180 - 138

14x = 42

Divide each side by 14.

14x / 14 = 32 / 14

x = 3

Then substitute the value of x back into the equation.

128 + 5 (3) + 10 + 9 (3) = 180

128 + 15 + 10 + 27 = 180

180 = 180

So, x is 3 degrees.

A triangle = 180

so 138 + 14x = 180

14x = 42

x = 3