Alright, ready to do some subtraction? We're taking 86109 and subtracting 78359 from it.

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

Step 2: We'll start by subtracting the digit 5 and the borrow 0 from 0 in column 2 and get -5.
We add -5 to 10 and get 5 as the next digit of the result.

Step 3: We'll start by subtracting the digit 3 and the borrow 1 from 1 in column 3 and get -3.
We add -3 to 10 and get 7 as the next digit of the result.

Step 4: We'll start by subtracting the digit 8 and the borrow 1 from 6 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 7 and the borrow 1 from 8 in column 5 and get 0.
0 is the next digit of our result.

So, 86109 - 78359 = 7750.