Chemistry help -- decomposition and rate equation k value?

[Monicaa]

Acetaldehyde decomposes when heated to yield methane and carbon monoxide
according to the equation:
CH3CHO(g) CH4(g) + CO(g)
Determine the rate equation and a numerical value for k from the following data:
t (s) CH3CHO M
0.00 1.75 x 10-3
10.00 7.80 x 10-4
15.00 6.36 x 10-4
20.00 5.41 x 10-4
30.00 4.20 x 10-4
40.00 3.44 x 10-4
50.00 2.93 x 10-4
60.00 2.55 x 10-4



Any suggestions?? Thank you soo much!!