Mupad - using brackets in statements

This might be a silly question, but can anybody explain why this assignment in Mupad does not produce an error:

a:=1000(9-x)

I am trying to show students most common errors, and this was supposed to be an example of how they need to always use multiplication sign, however Mupad obviously thinks this is a valid command and assigns a = 1000. What does it think (9-x) is then?

Answer 1

[Walter Roberson]

MuPAD tries to be smarter about recognizing implied algebraic operations, so it is probably treating that as a multiplication, 1000*(9-x)

There are some other stranger possibilities that I cannot test as I do not have Mathwork's Symbolic Mathematics Toolbox

Answer 2

[Lana]

Many thanks, however I do not think that Mupad treats it as a product - as x is not defined. I am more inclined to think that it treats is as an index or something but wanted to see if anybody knows for sure...