I ma working on a mastering physics assingment and got 2/3 parts done but I am having trouble on the last question that I thought was simple.

The problem reads

Find numerical values for

and

in seconds and meters for the (reasonable) values v0 = 26.8 m/s and a = 50m/s^2

my equation for tmax is:

tmax = v0/a

and Dstart

Dstart = 1/2* a * tmax^2

I thought I could just plug in the numbers in each equation but mastering physics keeps telling me its wrong. Can anyone give me a hint on what I might be doing wrong?