chemistry
posted by will .
I am having a hard time with this one not sure how to set up the problem.
A gas can holds 1.7gal of gasoline. What is this quantity in cubic centimeters?
I know that 1gal=3.785L
I know that 1L=1000cm^3
I have tried 1.7gal*3.785L/1gal=6.4345cm^3.
I just can not figure out what I am doing wrong.

The other two questions that I can not set up for conversions is
8.86*10^11m converted to gigameters
1.57*10^10m converted to picometers 
Your first one is great but you stopped too soon.
1.7 gal x (3.785L/gal) = 6.4345 L (Look at the units. gal cancels and you are left with L. Now you convert to cm^3 by
6.4345 L x (1000 cc/1L) = 6,434.5 cc.
There are two significant figures in the number of 1.7 gal; therefore, you should round the final answer to 2 places. That would be 6,400 cc.
There are 10^9 m in 1 Gm.
There are 10^12 pm in 1 m. 
I am still lost on setting up the last 2.

So do I set this up as:
8.86*10^11m (1Gm/10^9m)=8.86*10^11/10^9 since my meters cancel? Which then gives me 8.86^20 
Your set up is right. Your math is wrong.
That gives you 8.86 x 10^2 = 886 gigameters. (and you were smart to set up up that way to make the meters cancel and leave gm.) When you divide exponents you subtract; therefore 10^11/10^9 = 10^2.