The listed coordinates are dummy ones - don't try to go there. You will have to use some high-school algebra to calculate the true coordinates. Graphical solutions are unlikely to be accurate enough unless you have a very large piece of paper!
The following four caches by Grandalf lie at the four corners of a quadrilateral. You first need to find the Latitude-Longitude coordinates for these four caches:
Broomstick Basecamp (GCN6CT)
Possum Palace (GCN3T7)
Quarry Queerie (GCN8JY)
Simply Sudoku (GCP7VX)
NB:- Simply Sudoku is also a puzzle cache, and you must use the coordinates of the final cache from the Sudoku solution - don't use the listed coords.
From the intersection of the two lines joining opposite corners of the quadrilateral, go 46 metres on a grid bearing of 220 degrees to determine the Qurious Quadrilateral cache coordinates. The cache is a 400ml camo snaplock, with initial contents of logbook, pencil, sharpener, badge, bootlaces, spongy waterbomb, UK 3pence coin, French 10centime coin, and silica gel sachets.
Nearby is a seat dedicated to the memory of Rob Hall, a Kiwi mountaineer who died while guiding on Mt Everest in May 1996. The seat faces due west, looking out towards the mountains, and is surrounded by Buddhist prayer flags from the Himalayas.