$Pr(-5)*(-5 - 0)^2 + Pr(O)*(0 - 0)^2 + Pr(5)*(5 - 0)^2 = 24$
$25*Pr(-5) + 0 + 25*Pr(5) = 24$
$25(Pr(-5) + Pr(5)) = 24$
$Pr(-5) + Pr(5) = 24/25$
$(-5 * Pr(-5)) + (0 * Pr(0)) + (5 * Pr(5)) = 0$
$(-5 * Pr(-5)) + (5 * Pr(5)) = 0$
$5(-Pr(-5) + Pr(5)) = 0$
$-Pr(-5) + Pr(5) = 0$
$Pr(-5) = Pr(5)$
Since they are equal to one another, can I say that: $Pr(-5) = Pr(5) = 12/25 ?$