Add the following numbers:

1110 1011 101 + 101 1111 + 1111 =

Not sure if the question was quoted properly, because the last group of the first number has only three digits.

To add two binary numbers, we add a digit at a time just like in decimal, using the following rule:

0+0=0
0+1=1
1+0=1
1+1=0 with a carry of 1

So to add 101 to 111 we would have
101
+111
____
1100