Help me i just need this one

x = 12

Step-by-step explanation:

An exterior angle of a triangle is equal to the sum of its opposite interior angles in a triangle

∠CBV is an exterior angle and ∠BCD and ∠CDB are ∠CBV's opposite interior angles

This means that ∠BCD + ∠CDB = ∠CBV

If we are given that ∠CBV = 9x - 3, ∠BCD = 5x + 15 and ∠CDB = 30

Then 9x - 3 = 5x + 15 + 30

                    ^ (Note that we just created an equation we can use to solve

                        for x )

We then use the equation we created to solve for x

9x - 3 = 5x + 15 + 30

step 1 combine like terms

30 + 15 = 45

we now have 9x - 3  = 5x + 45

step 2 add 3 to each side

-3 + 3 cancels out

45 + 3 = 48

we now have 9x = 5x + 48

step 3 subtract 5x from each side

9x - 5x = 4x

5x - 5x cancels out

we now have 4x = 48

step 4 divide each side by 4

48 / 4 = 12

4x / 4 = x

we're left with x = 12

30+5x+15=9x-3

9x-5x =45+3

4x=48

x =12