1. The problem is to simplify the sum of three binary numbers: $1101_2 + 101_2 + 11_2$ and convert the result to decimal. 2. Recall that binary numbers are base 2, and to convert a binary number to decimal, multiply each bit by $2^{position}$ starting from 0 on the right. 3. Convert each binary number to decimal: - $1101_2 = 1\times2^3 + 1\times2^2 + 0\times2^1 + 1\times2^0 = 8 + 4 + 0 + 1 = 13$ - $101_2 = 1\times2^2 + 0\times2^1 + 1\times2^0 = 4 + 0 + 1 = 5$ - $11_2 = 1\times2^1 + 1\times2^0 = 2 + 1 = 3$ 4. Add the decimal equivalents: $13 + 5 + 3 = 21$ 5. Therefore, the sum of $1101_2 + 101_2 + 11_2$ in decimal is $21$.