The decimal equivalent of the binary number $(1101{)}_2$ is

To convert a base-2 binary number $(1101{)}_2$ into its base-10 decimal system equivalent, expand each bit position value by multiplying it by its corresponding power of $2$:
$$(1101{)}_2=(1\times 2^3)+(1\times 2^2)+(0\times 2^1)+(1\times 2^0)$$
$$(1101{)}_2=(1\times 8)+(1\times 4)+(0\times 2)+(1\times 1)$$
$$(1101{)}_2=8+4+0+1=13$$