Unfortunately, the English statement can be interpreted two ways.
1. 4 times (a number decreased by 8) = 40
Then (a number decreased by 8) is 40/4 = 10 and the number is 18.
2. (4 times a number) decreased by 8 = 40
The (4 times a number) = 40 + 8 = 48 and the number is 12.
_____
The order of operations requires you interpret
4×n - 8 = 40
in the latter sense. However, there is nothing in the English to indicate that interpretation should be used instead of 4×(n - 8) = 40.
