Can you give me some help with this question im not sure how to even start

in a reaction A to P
the mass of A at any given time T is Mt and the rate of transformation of A at time T is prportional to Mt given that the original mass of A is 130g and that 50g has been transformed after 120 seconds

form and solve a differential equation relating Mt to t
and find the mass of A transformed over a 300sec period

Response can be found here:

http://www.jiskha.com/display.cgi?id=1259495063