125\(_x\) = 20\(_{10}\) 1 x X\(^2\) + 2 x X\(^1\) + 5x X \(^0\) = 20 X2 + 2X + 5 = 20 X\(^2\) + 2X - 15 = 0 (X + 5)( X - 3) = 0 X + 5 implies X = -5 X - 3 implies X = 3 But X cannot be negative ∴X = 3