Question

Diana si Matei au 10 bile.Daca Diana ii da o bila lui Matei si Matei ii da 2 bile Dianei vor avea acelas nr de bile.Cite bile are fiecare copil?

Answer 1

d+m=10 bile
d-1+2=m+1-2
d,m=? bile
-1+2=+1
d|----------|----|
+1-2= -1
m|-----------|
=>d+1=m-1
d+m=10 bile/-1
d-1+m-1=10-1
d-1+d+1=9
2d+1=9
d=4
m=6
V:4-1+2=6+1-2
5=5 ( A )

Answer 2

d + m = 10 
 d - 1 + 2 = m +1 - 2
d +1 = m - 1 
d +2 = m
Deci m = d+ 2
d+2 + d = 10
2d=8
d=4 si m = 6