What is the correct way to write *= in Swift 2?

Question

iOS

Hello!
A very stupid question, but still:
Why, for example, the entry:

result = 10
result *= 2 + 1

gives the answer 30 and not 21? Isn't it the same as result = result * 2 + 1? If not, please explain how to correctly write the abbreviated version.

Answer 1

The order of operators is the same in almost all languages. 30 is the correct result
There are also += -= /= etc