Question

What is the value of x?

Answer 1

x=21

since there are 180° in a triangle you just have to make sure its equal,so it would be :
(21-4)+(3 *21)=100°
17+63+100=180

there for x equals 21

Answer 2

x=21

x-4 + 3x +100=180

x + 3x =84(180-100-4)

4x=84

x=21

x-4=17

3x21=63

100+21+63=180