I understand that it means that out of every 10 hours, a cat spends 7 sleeping (not 7 hours in a day).
this means that a cat is sleeping

a percentage stays constant, this means that a cat sleeps 70 % of each 10 hours, but also 70% of the day.
Before we do this problem, let's go over a little algebra terminology.
The number in front of your variable is called your <em>coefficient </em>and notice that the <em>x</em> at the end of the problem does not have a coefficient.
When that happens, when there is no number in front of your variable, you can put a 1 there to fill that position. So -x can be thought of as -1x.
Next let's change all our minus signs to plus negatives.
So the problem reads 3x + 5 + 7x + -3 + -1x + 2.
Now let's simplify this by combining like terms.
We can combine our "x" terms first.
3x + 7x + -1x simplifies to +9x.
Now, 5 + -3 + 2 simplifies to 4.
So our answer is 9x + 4.
B. As the x-values increase, the y- valuebtend to decrease.
If you want to see if they are equivalent just substitute any number such as 2, so 2.5(2) = 5 and 2 + 5 = 7, so they are not equivalent (THIS IS TRUE UNLESS YOU DIDNT PUT THE X VALUE IN THE QUESTION)