Which expression is equivalent to (3c)-2?

Assuming that the notation there is meant as:

then the answer would be 1/(9c²)

If the -2 is indeed just subtraction and not an exponent, then it is simply 3c - 2

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.