Solving for Height and Distance: Janet's Displacement Speed Calculation

[halo9909]

Homework Statement

Janet jumps off a high-diving platform with a horizontal velocity of 3.1 m/s and lands in the water 3.0 s later. How high is the platform, and how far from the base of the platform does she land?
m (height)
m (distance from platform)

Homework Equations

horizontalV*t=D

The Attempt at a Solution

I have got the distance from platform to be 9.3m using the forunla, but am unsure of the height like what formula to use

 

[LowlyPion]

Here are some kinematic formulas that you might find useful.
https://www.physicsforums.com/showpost.php?p=905663&postcount=2