Question 269789
x-3y+7z+w=11
2x+4y+6z-3w=-3
3x+2y+z+2w=19
4x+y-3z+w=22 
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Looks like 4.
Determinant = -535
w = 3
x = 5
y = -1
z = 0
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I made an Excel sheet to do these. Doing them manually is tedious and error-prone.
There are sites that will solve up to a 10 by 10 that I've seen.