significant figures

[syed786]

evaluate the following expressions and express the answer with the appropriate number of significant figures.

A) 320.55-(6104.5/2.3)
B.)[(285.3 x 10^5)-(1.200 x 10^-3)] x 2.8954
C.) (0.0045 x 20 000.0)+(2813 x 12)
D.) 863 x [1255-(3.45 x 108)]


im not sure if my answers are right, i got: a) -2333.55
b.) 82605762= 8260
c.)33846=3385
d.) 761511.2= 761

PLEASSSSE help me as soon as possible!!!!!!!