x+3x=20
x+(x-20)+3x=180
3(x+20)-4x=10
Помогите пожалуйста

4x = 20x = 20/4x = 5x + x - 20 + 3x = 1805x = 180 + 205x = 200x = 200/5x = 403x + 60 - 4x = 10- x = - 50x = 50