Hey there! :D
3612= 6s+s
Let s= how heavy the packet of sugar is. Since the flour is 6 times heavier, and they both equal 3612 together, we can set up the equation like that. 
3612= 7s
Divide both sides by 7. 
s= 516
Multiply that by 6 for the mass of the flour. 
516*6= 3096
The mass of the flour if 3096. 
I hope this helps!
~kaikers