Oxidation number of the ff elements.

a. CaH2 oxidation no. for Calcium
b. Al2O3 oxidation no. for Aluminum
c. Al(BrO3)3 oxidation no. for Al
d. Al(BrO3)3 oxidation no. for Br
e. H2SO3 oxidation no. for S
f. H2SO4 oxidation no. for S
g. CO oxidation no. for C
h. (CO3)2- oxidation no. for C
i. (C 2O4)2- oxidation no. for C
j. CaC2 oxidation no. for C

As much as I would like to answer this on my own, our brilliant teacher decided to give us homework over Christmas break without discussing how we're supposed to get the answers.

Okay, we can do this the easy way, or the hard way.
Hard way ( you have to think):
Each compound balances, that is, their oxidation numbers of each element together will add up to zero.Also, every oxygen in that list, every O in other words, has an oxidation number of -2.
Every H has a +1 number.
Example: Al2O3 3 times -2 is -6 . Must add to 0, so Al must be +3. (2 x 3)+(3 x -2) = 0, so +3 is correct.

Easy way:
a: -2 b:+3 c:+3 d:+5 e: +4 f: +6 g: +2 h: +4 i: +3 j:+1