Create an equation. Since all of the angles of any triangle add up to 180 degrees, our equation will be:
7x+25+9x+25+5x+25=180.
Now, jus solve for x.
Combine like terms
21x+75=180
Subtract 75 on both sides to further simplify.
21x=105
Finally, divide both sides by 21 to isolate x.
X=5
Hope this helps!
