we are given three angles
first angle =x-4
second angle =3x
third angle =100
we can see that this is a triangle
and we know that
sum of all angles in any triangle is always 180
so,
first angle + second angle + third angle =180
now, we can plug values
and we get
[tex] x-4+3x+100=180 [/tex]
now, we can solve for x
[tex] 4x+96=180 [/tex]
[tex] 4x+96-96=180-96 [/tex]
[tex] 4x=84 [/tex]
[tex] x=21 [/tex]................Answer
