∠C=x
∠B=х+20
∠А=(х+20)*2
∠А+∠В+∠С=180
х+х+20+(х+20)*2=180
х+х+20+2х+40=180
4х+60=180
4x=180-60=120
x=120/4=30
∠C=30
∠B=30+20=50
∠A=50*2=100
Если что-то не понятно, спрашивай)
1) x - 7 8/11 = 2 5/11,
x = 2 5/11 + 7 8/11,
x = 27/11 + 85/11,
x = 112/11.
2) 3 7/17-( x+1 4/17) = 1 9/17
58/17 - x - 21/17 = 26/17
37/17 - x = 26/17
- x = 26/17 - 37/17
-x = -11 / 17
x = 11/17