How do you solve?

Question

4.9t^2 - 13.5t - 60 = 0

Answer 1

4.9t²-13.5t-60=0, t=(13.5±√(182.25+1176))/9.8=(13.5±√1358.25)/9.8=5.1382 approx (using the quadratic formula). There's another solution t=-2.3831, but this problem looks like a projectile problem where t represents time (positive), so I guess the answer would be t=5.1382 seconds.