Answer: 
Step-by-step explanation:
The first thing you must remember is the mulplication of signs. You know that:

You can observe that the number inside the parentheses is positive (+) and the sign that is outside the parentheses is negative (-), therefore, when you multiply these signs you get a negative sign (-). Then you get:

Now, you need to add these numbers. And the result obtained is:

subtract 6.4 from 25 = 1.3c + 18.6
Let the 2 equal lengths be represented by 2p. Then you can write the equation of ratios
p 2p
---- = -------
16 x+4
which simplifies to
1 2
----- = ------
16 x+4
then x+4 = 32, and x = 28 (answer)
There are 14 groups of days are in 1 week.