Divide with a full worked long-division layout, quotient and remainder.
Long division works one digit at a time from left to right. At each step you bring down the next digit of the dividend, ask how many times the divisor fits into the running total, subtract that multiple, and carry the leftover. The digits you wrote across the top form the quotient; the final leftover is the remainder.
Division identity
Dividend = Divisor × Quotient + Remainder
The remainder is what's left over after dividing as many whole times as possible. If you divide 17 cookies equally among 5 people, each person gets 3 (the quotient) and 2 cookies are left over (the remainder).
Multiply the quotient by the divisor and add the remainder. The result should equal the dividend. For example: 7 × 125 + 0 = 875 ✓.
When there is a remainder, the 'decimal extension' setting adds zeros to the dividend and continues dividing, giving you a decimal approximation. Set it to 0 if you only want the integer quotient and remainder.