a
a + (b + c) = (a + b)
+ ca(b + c) = ab + ac
y = 18
163 ·7 – 7 · 63 = 7 (163 – 63) = 7 · 100 = 700
2 вариант
a + (b + c) = (a + b) + c
a + b = b + a
a(b + c) = ab + ac
y = 10
63· 7 + 37·7 = 7 · (63 + 37) = 7 · 100 = 700