Answer:


Explanation:
In order to find the measure of our angle, we have to note angle relationships.
All angles in a triangle will add up to 180°
This means all the angles in this triangle will equal 180, or:

We can simplify this equation down to find the value of x.
Combine like terms:

Add 20 to both sides:

Divide both sides by 10:

Now that we know the value of x, we can substitute it into the equation for each angle to find it's value.
m∠H:

m∠I

m∠J

To further prove this is right, we would know that all the angles add up to 180°.
, so we should be right.
Hope this helped!