Question

2*7^x+1-6*7^x-1-7^x=85

Answer 1

$2 \cdot 7^{x+1}-6 \cdot 7^{x-1}-7^x=85 \\ {7}^{x} (2 \cdot 7 - \frac{6}{7} - 1) = 85 \\ {7}^{x}(14 - \frac{13}{7} ) = 85 \\ {7}^{x} ( \frac{85}{7} ) = 85 \\ {7}^{x} = 7 \\ x = 1$