Number Theory

We can convert both numbers to base 10, add them up, and convert them back. 

First, let's convert the two. We have

$(357)_8 = (3 × 8^2) + (5 × 8^1) + (7 × 8^0) = (239)_{10}$

$(501)_8 = (5 × 8^2) + (0 × 8^1) + (1 × 8^0) = (321)_{10}$

Adding our two results up, we get the sum

$321+239=560$

Now, we must convert this into base 8 again. 

We get $560_{10}=1060_8$

So our final answer is 1060. 

Thanks! :)