3х+15х-8=18х-8 при х=2 18*2-8=36-8=28 ответ:х=28
4,7-2.5y-12.4=4.9
4.7- 12.4- 4.9=2.5y
-12.6=2.5y
-2.5y=12.6
y=-5.04
1 )5car 42мин
2) 4car 42мин
705*25*4 = 705*100 = 70500
28*25 = 7 * 100 = 700
8*49-8*41 = 8*(49-41) = 8*8 = 64
27*99+27 = 27*(99+1) = 27*100 = 2700