How can you use an equation to find an unknown value in a proportional relationship?

Well if you already know how to write an equation for a given set of proportions, then all you have to do is replace the unknown value with x, and then cross multiply and solve the equation. One important thing to remember is that for each proportion the numerator and the denominator have to be of the same units in the equation.

60

step-by-step explanation:

every triangle measures a total of 120 degrees. you have to find angle c. we know that isosceles triangles angles are equal. 60 degrees plus 60 degrees gives you 120.