this is a text book question that i cannot figure out.

Question

the decomposition of dimethyl ether at 510 degrees is a first-order process with a rate constant of 6.8*10^-4.
(CH3)2O(g)--> CH4(g) + H2(g) + CO(g)
if the partial pressure of (CH3)20 is 18kPa, what is its partial pressure after 1420sec.

Answer 1

I think you can simply substitute into
ln(Po/P) = kt and solve for p.