Осталось х л, продали 7х л
7х + х = 80
8х = 80
х = 10(л) - осталось продать
10 * 7 = 70(л) - продали
1. 1 7/8 + ( 1 3/5 + 1 1/8) = 5 1/10
1) 1 3/5 +1 1/8 = 1 24/40 + 1 5/40 = 2 29/40
2) 1 7/8 +2 29/40 = 1 35/40 + 2 29/40 = 3 + 84/40 =
=3+ 2 4/40 = 5 4/40 =5 1/10
2. 7 1/2 - (1 3/8+1 1/2) =4 5/8
1) 1 3/8+ 1 1/2 =1 3/8 +1 4/8 = 2 7/8
2) 7 1/2 - 2 7/8 = 7 4/8 -2 7/8 =
= 60/8 - 23/8= 37/8= 4 5/8
3. 9 1/16 - (5/8+7/16)=8
1) 5/8+7/16= 10/16 +7/16 = 17/16= 1 1/16
2) 9 1/16 - 1 1/16 = 8
4. 7 3/4 + (2 7/8 - 1 3/4)= 8 7/8
1) 2 7/8 - 1 3/4 = 2 7/8 -1 6/8 = 1 1/8
2) 7 3/4 +1 1/8 = 7 6/8 + 1 1/8= 8 7/8
1) 7*2,1+3,8*9,6=51.18
Ответ 51,18
Х+у=у+15 х+у=х+35
х=у+15-у у=х+35-х
х=15 у=35
х*у=15*35=525