let be A(-3,3), B(t,-1), and C(8,6), three points are collinear means the vector vecAB and vecAC or vecAB and vecBC are collinear
for example
AB and AC are collinear,equivalent of det(vecAB, vecAC )=0
vecAB =(t+3, -4) and vecAC = (11, 3)
det(vecAB, vecAC )=3(t+3) +11(4)=3t+9 +44=0, it implies t= - 53/3
so t = - 53/3
