Explicação passo-a-passo:

a)

180°= x+40°+7x+3°+6x-3°

180°= x+7x+6x+40°

180°= 14x+ 40°

180°-40°= 14x

140°= 14x

140°÷14=x

10=x

10+40=50

7×10+3=73

6×10-3=57

b)

180°= 10x+5°+8x-1°+4x

180°= 22x+4°

180°-4°= 22x

176°=22x

176÷22=x

8=x

10×8+5=85

8×8-1=63

4×8=32

c)

180°= 4x-3°+x+13°+3x+10°

180°=8x+20°

180°-20°=8x

160°=8x

160°÷8=x

20=x

4×20-3=77

20+13=33

3×20+10=70