A man 50kg runs at a speed of 9m/s, stops for 0.3s, then makes a high jump to a height of 1.5m. What is his acceleration at the start of the jump?

Show us yor attempt at solving this and we'll give you some guidance if needed. But given the fact that the man stopped before jumping - what do you think that means with respect to the any effect on his acceleration when he makes the jump?

I calculated the velocity at the start of the jump by equating the P.E and K.E and got 4.95m/s. He pushes his feet for 0.3s before taking the jump. The question asks for his acceleration.
Thanks for trying to help me!

If you assume that his acceleration is constant during that 0.3 seconds, then you can use

a = delta v/time