7. 13•0•P = 0
Explanation : Anything times 0 will equal 0!
8. 7•z•0 = 0
Explanation: Anything multiplied by 0 will equal 0.
9. 2.5•w•1= 2.5w
Explanation: Anything times one equals that.
10. 1•x•19= 19x
11. (t+3)+ 0= t+3
12. 0+(g+4) =g+4
Quite simple but uses a little bit of thinking! (: