depending on what course you are taking, you can use limits to solve most of these, but if not, you simply say they do not exist.
a. 1/0 Divide by 0, does not exist
b. 1/INFINITY does not exist
c. INFINITY/0 divide by 0, does not exist
d. 0/INFINITY = 0 (0 divided by anything is 0)
e. INFINITY/1 = INFINITY (dividing in 1 piece is just itself)
f. INFINITY/INFINITY = 1 (x/x is always 1)
g. 0/0 = divide by 0, does not exist