+  0  1  2  3  4  5  6  7  8  9 

0  0  1  2  3  4  5  6  7  8  9 
1  1  2  3  4  5  6  7  8  9  10 
2  2  3  4  5  6  7  8  9  10  11 
3  3  4  5  6  7  8  9  10  11  12 
4  4  5  6  7  8  9  10  11  12  13 
5  5  6  7  8  9  10  11  12  13  14 
6  6  7  8  9  10  11  12  13  14  15 
7  7  8  9  10  11  12  13  14  15  16 
8  8  9  10  11  12  13  14  15  16  17 
9  9  10  11  12  13  14  15  16  17  18 
Align the two numbers at the decimal point. Pad to the left and right if required. Start at the LSD of each number. Start with a carry in of 0 While there are digits left Add the two digits and the carry in. Write down the "ones" result Make the carry out the carry in of the next digit. Move to the left If there is a nonzero carry out, write it down

+  0  1 

0  0  1 
1  1  1 0 
2542_{7} +1665_{7} 5+2 = 7, but we don't have seven in base 7 so it is 10 4+6+1 = 7+4 = 14_{7} 6+5+1 = 7+5 = 15_{7} 2+1+1 = 4 111 2542_{7} +1665_{7} 4540