1) (5,1a+1,8)-3,4a , a = 1 , a = 1,5
2) (x-18,2)+3,8 = 15,6
3) ч+16,23-15,8 = 7,1

1)1.7a+1.8 a=1 1.7×1+1.8=3.5 а=1.5 1.7×1.5+1.8=4.352)x=15.6-3.8+18.2 x=303)ч=7.1-16.23+15.8 ч=6.67