I)
/__________F______/________B_______/......+ 4....../
23 elevi
/________F_____/______F________/______B______/ 27 elevi
27:3 = 9;
9 - 4 = 5 băieți;
9 x 2 = 18 fete
II)
/______a_____/_____b_____/______c______/ = 418;
/____c____/____c___/ a = 2c;
/_c/2 - 2_/ ; b = (a/4):2 - 2 = c/2 - 2;
2c + c/2 -2 + c = 418;
3c + c/2 = 418 + 2;
7c = 840;
c = 120;
a = 2x120 = 240;
b = 120:2 - 2 = 60 -2 = 58;