XYZ Coordinates to Earth Plot

Lost in 3D kind of explains my knowledge of advanced Excel. I've been trying to solve it on paper and can't get my head around the complexity. Hopefully some folks can help!
I have data from 5 satellites and I'd like to know how to calculate the position on Earth of the receivers coordinates, XYZ,
I know how to convert geodetic coordinates to Cartesian if necessary.

Please, can anyone help?


Satellite View.jpg
Satellite View Data.jpg
or Cartesian Coordinates:
ECEF COORDS X Y Z
SAT1 2926991.38342522 -3882838.58596944 4144244.87430255
SAT2 3268136.54260175 -4639752.26938107 2944623.86418239
SAT3 -347247.81198599 -5693759.79190739 2888355.61305460
SAT4 3864424.69757511 -2592871.37042505 4375986.84769265
SAT5 -1491397.01293895 -3254491.69640659 5285985.02139871

Looking for more classroom geometry as the assumptions don't include any real life error. Some assumptions:
•All four signals reached your GPS receiver simultaneously
•The waypoint is at sea level
•The Earth's atmosphere has no effect on the GPS signal
•The Earth is a perfect sphere, with a radius of 6370 kilometers
•The speed of light is 3.00E+08 meters per second
•Your GPS receiver has no time differential error"