Question

Help please !!!!! Super hard

Answer 1

The image is really unclear but I will assume that the number of teams given = 66
and the formula is
$n = \frac{ {t }^{2} - t }{2}$
plug in the number of teams
$66 = \frac{ {t}^{2} - t }{2}$
multiply both sides by two
$132 = {t}^{2} - t$
subtract 132 from both sides and factor
t = 12