If x, y, and z are positive real numbers satisfying:
log x - log y =a
log y - log z = 15
log z - log x = -7
where a is a real number, what is a?
log x - log y = a
Add the last two equations
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log y - log x = 8 multiply through by -1
log x - log y = -8 = "a"
+166 
