What is the solution to log sub 5 of open paren 10 x minus 1 close paren is equal to log sub 5 of open paren 9 x plus 7 close paren ?

Since logarithms with the same base are equal only when their positive arguments are equal, set 10x − 1 = 9x + 7. Subtract 9x and add 1 to both sides to get x = 8. This value makes both logarithm arguments positive, so the solution is choice C, x = 8.

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