Question

How do i know when to add or subtract in an angle equation?

Answer 1

Answer:

17

Step-by-step explanation:

< ABD = <ABC + < CBD

Substitute in what we are given

87 = 9x-1 +   6x+58

Combine like terms

87 = 15x +57

Subtract 57 from each side

87-57 =15x +57-57

30 = 15x

Divide by 15

30/15 =15x/15

2=x

We want to find <ABC

<ABC = 9x-1

         = 9*2-1

         =18-1

      =17