Răspuns:
Explicație pas cu pas:
a) x=0
b) imposibil
c)x=5
d) y=0, x = 0,1,2,3,4,5,6,7,8,9 (10 nummere)
6) 18 = 2*9
y = 0,2,4,6,8
5+7+x +y =9k ; x = 9k-12-y
y=0, x = 9*2-12-0 = 6
y=2, x = 9*2-12-2 = 4
y = 4, x = 9*2-12-4 = 2
y = 6 , x = 9*2-12-6=0
x = 9*3-12-6=9
y = 8, etc