Solve the Subtraction Problem: 48 Units Minus 9 Units

To solve this problem, we need to subtract 9 from 48. This involves simple subtraction:

• Write the numbers vertically, aligning the decimal if necessary, though here they are whole numbers:
  48
  $-$
  9
• We start from the rightmost column (units place). Subtract 9 from 8:
• Since you cannot subtract a larger number from a smaller one without getting into negative numbers, you should consider regrouping.
• We take 1 from the tens place, turning the 4 (in 48) to 3, and the 8 (becomes 18).
• Subtract 9 from 18, which gives 9.
• The remaining in tens column is 3 (because we reduced it by 1).

By combining these, the subtraction of 9 units from 48 units gives us:

$39$

Therefore, the solution to the problem is $39$, which matches the third choice given.