87421 ÷ 7 = 12488 R5
We're going to perform division on 87421 with 7 as the divisor.

Step 1:
7 goes into 8 1 times with a remainder of 1.
Write down 1 as next digit of of the result. 
Result so far: 1
Subtract 7 from 8 to get 1.
Bring next digit (7) of the dividend behind the 1 and repeat the process: 17 / 7

Step 2:
7 goes into 17 2 times with a remainder of 3.
Write down 2 as next digit of of the result. 
Result so far: 12
Subtract 14 from 17 to get 3.
Bring next digit (4) of the dividend behind the 3 and repeat the process: 34 / 7

Step 3:
7 goes into 34 4 times with a remainder of 6.
Write down 4 as next digit of of the result. 
Result so far: 124
Subtract 28 from 34 to get 6.
Bring next digit (2) of the dividend behind the 6 and repeat the process: 62 / 7

Step 4:
7 goes into 62 8 times with a remainder of 6.
Write down 8 as next digit of of the result. 
Result so far: 1248
Subtract 56 from 62 to get 6.
Bring next digit (1) of the dividend behind the 6 and repeat the process: 61 / 7

Step 5:
7 goes into 61 8 times with a remainder of 5.
Write down 8 as next digit of of the result. 
Result so far: 12488
Subtract 56 from 61 to get 5.

The final result is 12488 with a remainder of 5.