Evaluate the following expression: $4^7\times4^{-5}$47×4−5.
Evaluate the following expression: $8^{-10}\times8^{13}$8−10×813.
Evaluate the following expression: $5^2\times5^{-4}$52×5−4.
Simplify the following, giving your answer with a positive index: $2^3\div2^{-2}$23÷2−2