(1×2×3....×20)÷(1×2×3.....×19)

The expression (1×2×3....×20) ÷ (1×2×3.....×19) can be simplified as follows: (1×2×3....×20) ÷ (1×2×3.....×19) = 20 This is because all the terms in the numerator (1×2×3×...×20) cancel out with the terms in the denominator (1×2×3×...×19), leaving only the value of 20 in the numerator.