Use a common denominator to find-2/3 + -4/5

-22/15

Explanation:

the least common denominator is  15 so first you multiply -2/3 by 5 in both the numerator and denominator making it -10/15

Then you do the same to -4/5 except you multiply the numerator and denominator by 3 giving you -12/15

If you add -10/15+ -12/15 you get -22/15

the maxium height is 34m/s

not too sure thinking all accelerations are pointed down