18+(16-х)*8= и второе (4900: у-280): 60=7

1) 18+(16-х)*8=90

18+128-8x=90

146-8x=90

-8x=90-146

-8x=-56

x=7

2) (4900:у-280):60=7

(4900/y-280)*1/60=7

4900-280y/60y=7

4900-280y/60y=7, y 0

20(245-14y)/60y=7

245-14y/3y=7

245-14y=21y

-14-21y=-245

-35y=-245

y=7, y0

y=7