Question

What’s the value of x? and what’s the measure of angel JHK?

Answer 1

Because ∠GHI and ∠JHK are vertical angles, they're congruent. Therefore, set their angle measures equal to each other & solve for x.

`x+7=3x-21\\x-3x=-7-21\\-2x=-28\\x=(-28)/(-2) =14\°`

Substitute in the value of x to find ∠JHK:

`3x-21=3(14)-21=42-21=21\°`

Answer 2

x = 14

JHK = 21

Explanation:

The angles are vertical angles and vertical angles are equal

3x-21 = x+7

Subtract x from each side

3x-x -21 = x+7-x

2x-21 = 7

Add 21 to each side

2x-21+21 = 7+21

2x = 28

Divide by 2

2x/2 =28/2

x = 14

JHK = 3x-21 = 3(14) -21 = 42-21 = 21