Constant acceleration simultaneous equation

[bigjuicy]

Homework Statement

A pizza is being dropped from a height of 20 m. Another pizza is being thrown up at 30m/s from 0m(the one falling is above the one being thrown). At what position in the air will they meet?

a= -10m/s^2

Homework Equations

Im not sure but i think that some of the b5 kinematics equations would apply. I am pretty sure that this requires a simultaneous equation.

The Attempt at a Solution

first i had x=viT+1/2aT^2

i attempted to get all the t's to one side but got stuck at (2x/vi)/a=(t^2)/vi)+2t/a

i assumed that the t's must be equal. I am unsure whether or not i approached the problem correctly or not

 

[bigjuicy]

I appreciate you guys for looking at this but i think i got it:
so basically

you have two side

first equation = falling pizza:

x=0-1/2at^2

you set that one, equal to your thrown pizza: x=30-1/2at^2

set them equal to each other, then solve for t then use that t to solve for x