We've tried to keep the interface simple. Although there aren't brackets you can do sums that require them. For example, you could input:
25 * 8 = 400
and
3 * 10 = 30
You can then tap on the 400 to start a new calculation, followed by an operator and the 30, to do the following:
400 - 30 = 370
Essentially, anything on the screen that looks like a tile can be tapped on and used.