I need someone to answer this physics question sobs?

The height of a particle above the ground in such situations is h = -4.9t^2 + vt + h_1, where v is the original velocity of the particle (positive if moving up, and negative if moving down), and h_1 is the original height above the ground. So first write the height formula for each of your two particles, using the information in your question, then set the two equations equal to each other and solve for t. When you set the two equations equal to each other, you will have a quadratic equation in front of you; you need to know how to solve a quadratic. When you have solved for t, (that's the answer to a) ), then take this value for t and put it into either of the two formulas you wrote, and work out the height.