Any binary number can be converted to its decimal equivalent simply by summing together the weights of the various positions in the binary number which contain a 1.

1 1 0 1 1 (binary)

2^4+2^3+0+2^1+2^0

= 16+8+0+2+1
= 2710 (decimal)

and

1 0 1 1 0 1 0 1 (binary)

2^7+0+2^5+2^4+0+2^2+0+2^0
= 128+0+32+16+0+4+0+1
= 18110 (decimal)

You should noticed the method is find the weights (i.e., powers of 2) for each bit position that contains a 1, and then to add them up.