What does the operator -= do?

What does the operator -= do?

• A. Adds a value to a variable and assigns the result.
• B. Subtracts a value from a variable and assigns the result.
• C. Multiplies by a value and assigns the result.
• D. Divides by a value and assigns the result.

Answer: (B)

The subtract-assign operator first subtracts the right-hand side value from the variable on the left, then stores that result back into the left-hand variable. In other words, it’s the same as writing x = x - value. For example, if a variable starts at 10 and you do var -= 3, it becomes 7. This makes it convenient to decrease a variable by a certain amount in one step. It’s different from general subtraction, which computes a difference without saving it back; the compound form specifically updates the variable with the new value.

The subtract-assign operator first subtracts the right-hand side value from the variable on the left, then stores that result back into the left-hand variable. In other words, it’s the same as writing x = x - value. For example, if a variable starts at 10 and you do var -= 3, it becomes 7. This makes it convenient to decrease a variable by a certain amount in one step. It’s different from general subtraction, which computes a difference without saving it back; the compound form specifically updates the variable with the new value.