Ineed asap mary throws a ball vertically with a velocity of 29.4 m/s, as the figure indicates. what is the velocity in the 1st second? what is the velocity in the 2nd second?

You've been hearing "acceleration of gravity is 9.8 m/s²" for so long,
and you've heard it so many times, that you can recite it in your sleep.
But you're not clear on what it means or what to do with it.  If you were,
then you could answer this question in your sleep too.

It means:

When gravity is the only force on an object, it adds 9.8 m/s to
the object's downward speed every second.

If the object happens to be going up, then gravity makes it go up
9.8 m/s slower every second, until it stops going up.

When the object in the picture leaves Mary's hand, it's going up at 29.4 m/s.

After that, gravity is the only force acting on it, SO . . .

-- After 1 sec, it's rising 9.8 m/s slower.  That's (29.4 - 9.8) = 19.6 m/s.
In the first second of rising, its speed shrinks from 29.4 m/s to 19.6 m/s.

-- After 2 sec, it's rising ANOTHER 9.8 m/s slower. 
In the 2nd second of rising, its speed shrinks from 19.6 m/s to 9.8 m/s.

-- After 3 sec, it's rising ANOTHER 9.8 m/s slower.  (9.8 - 9.8) = 0 m/s.
In the 3rd second of rising, its speed shrinks from 9.8 m/s to zero.

After 3 seconds, it has completely run out of upward gas. 
Its upward speed has dwindled completely to zero, and
it starts falling.