Hi fabxx,

We have . Note that in the text it states, "at time , a ball was thrown upward from an initial height of feet" so we can let and . This yields . Call this equation . Also note in the text; " feet at the time " thus letting and we have . Define this as equation .

Now we have two equations with two unknowns, namely and ;

All that remains is to solve these two equations simultaneously finding and then subbing in and the values for and . Can you continue?