Răspuns :
a x (1 + 2 + 3 + .... + 14) = 210
a x 14 x 15/2 = 210
a x 7 x 15 = 210
a = 210/105 = 2
a x 14 x 15/2 = 210
a x 7 x 15 = 210
a = 210/105 = 2
a x (1+2+3+4+5+6+7+8+9+10+11+12+13+14)=210.
a x 14 x 15\2= 210.
a x 7 x 15= 210.
a= 210\105=2.
a x 14 x 15\2= 210.
a x 7 x 15= 210.
a= 210\105=2.