(18800:100)*25=4700
или
18800*0,25=4700.
Ответ:4700 марок.
5.6-6+1.2х=1.6х+0.4
1.6х-1.2х=5.6-6-0.4
0.4х=-0.8
х=-0.8:0.4
х=-2
1) 5a = 50 + a
2) d2 = d*10 + 2
3) m4m = m*100 + 40 + m
4) 86k = 800 + 60 + k
5) mn1 = m*100 + n*10 + 1
6) 16b = 100 + 60 + b
7) 9abc = 9000 + a*100 +b*10 + c
8) mnkl = m*1000 + n*100 + k*10 + l