Răspuns:
(11+22+33+…+99)/95 = x/4
[11 x (1 + 2 + 3 + ...+ 9)] / 95 = x/4
[11 x 9 x 10 : 2] / 95 = x/4
[99 x 5] / 95 = x/4
99/19 = x/4
19x = 99×4
19x = 396
x = 396/19