2:1/3=2*3=6 все пуговицы
6-2=4 маленьких пуговиц
А = торты.
b = кексы.
c = пироги.
а + b = 7
b + c = 9
a + c = 6
a + b – (b + c) = 7 – 9
a – c = – 2
a + c + a – c = 6 – 2
2a = 4
x
a = 2 – торты.
b = 7 – 2 = 5 – кексы.
c = 6 – 2 = 4 – пироги.
a + b + c = 2 + 5 + 4 = 11 штук – всего подарков.
12:35,.....................
5/8 + 5/24 = (15+5) / 24 = 20/24 = 5/6
1/2 - 1/8 = (4-1) / 8 = 3/8
3/4 - 1/12 = (9-1) / 12 = 8/12 = 2/3
11/15 + 7/30 и 3/4
11/15 + 7/30 = (22+7) / 30 = 29/30
29/30 больше 3/4