Solve Decimal Subtraction: Calculate 15.8 - 3.5

$15.8-3.5=$

To solve the problem $15.8 - 3.5$, we will perform decimal subtraction:

• Step 1: Align the decimal places.
  Write the numbers so their decimal points are lined up:
  $\quad 15.8\\ - \, 3.5\\ --------$
• Step 2: Subtract the numbers column by column.
  - Start from the rightmost digit (tenths place), $8 - 5 = 3$. Write $3$ under the line in the tenths place.
  - Move to the next left column (ones place), $5 - 3 = 2$. Write $2$ in the ones place.
  - The digit in the tens place $1$ moves straight down as there is no number to subtract from.
  $\quad 15.8\\ - \, 3.5\\ \underline{--------}\\ \quad 12.3$
• Step 3: Conclude with the final answer.
  The result of $15.8 - 3.5$ is $12.3$.

Therefore, the correct answer is: $12.3$.