10^2n+3 × 20^n × 5^n

Step:?

Answer:10^4n+3

change 20 to 10*2

and 5 to (10/2)^n= 2^-n * 10^n

then

10^(2n+3)*2^n*10^n*10^n *2^-n

2^0 * 10^(2n+3+n+n )=10^(4n+3)