The missing term in the denominator is
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[tex]\frac{7^{16} }{7^{12} }= \frac{7^{16-34} }{7^{12-34} } =\frac{7^{-18} }{7^{-22} } = 2401[/tex]
so the missing term in the denominator is 7^(-22)
ok done. Thank to me :>