Question

S=
ut +
at²
150 = 20t + 1/2 + (-1) t²

Answer 1

Explanation:

t^2/2+20t=150

t^2+40t=300

t^2+40t-300=0

t^2-30t-10t-300=0

t(t-30)-10(t-30)

so,t=30 sec

hope it helps you

Answer 2

Answer:

I think upper answer is right