Compute the weakest precondition for the following sequence of statements by using the postcondition.

y=y*5;

if(y<0) y=y+2;

else y=y-2;

{y<12}

I am not sure about which precondition or postcondition belongs to which statement.I fail to solve any questions which represent such sequences(syntax ).Kindly solve this question in steps and advise on how I should approach such questions.