2003 AMC 10B Problem 9

Writing everything base $5,$ the left side is $5^{-4}$ and the right side is $$5^{\frac{48-26-34}{x}}=5^{-\frac{12}{x}}.$$ Setting exponents equal, $-4=-\dfrac{12}{x},$ so $x=3.$ Thus, the correct answer is B.