Zero property because you are using zeros to multiply
Yes, they are. They cannot happen both. Every time that you roll a cube you can get only one number, then if you roll a 4 you cannot roll a 3 at the same tiem, and if you roll a 3 you cannot roll a 4 at the same time.
Mutually exclusive events cannot happen at the same time.
For the first problem, a "fifth" means divided by 5, so "four-fifths of b" means

or

Subtract means to take away, so "6 subtracted from" means to "take away 6" or -6
As such, the answer to the problem would be

The rest the problems are also just translating English to math.