The difference between m and r from the given expressions is 8
Given the following exponents
x^m/x^5=x^7
x^m = x^5 * x^7
x^m = x^12
Equate the powers
m = 12
For the expression
(x^r)³ = x^12
x^3r = x^12
3r = 12
r = 4
Take the difference
m - r = 12 - 4
m - r = 8
Hence the difference between m and r is 8
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