Let's dive into this subtraction. We'll start with 773909 and subtract 66094 from it.

Step 1: We'll start by subtracting the digit 4 and the borrow 0 from 9 in column 1 and get 5.
5 is the first digit of our result.

Step 2: We'll start by subtracting the digit 9 and the borrow 0 from 0 in column 2 and get -9.
We add -9 to 10 and get 1 as the next digit of the result.

Step 3: We'll start by subtracting the digit 0 and the borrow 1 from 9 in column 3 and get 8.
8 is the next digit of our result.

Step 4: We'll start by subtracting the digit 6 and the borrow 0 from 3 in column 4 and get -3.
We add -3 to 10 and get 7 as the next digit of the result.

Step 5: We'll start by subtracting the digit 6 and the borrow 1 from 7 in column 5 and get 0.
0 is the next digit of our result.

Step 6: We'll start by subtracting the digit 0 and the borrow 0 from 7 in column 6 and get 7.
7 is the next digit of our result.

So, 773909 - 66094 = 707815.