Question 10 is attached!
for all your !

8r + 2r - 7r = 18
10r - 7r = 18
3r = 18
r = 18/3
r = 6

Good morning! ~

r = 6 

And this is why;

First, when we have our equation, were going to simplify. 

So we have 

8r + 2r - 7r = 18

Combining like terms;

(8r + 2r - 7r) = 18

3r = 18

Now we are going to divide each side of our equation by 3 

3r/3 = 18/3

r=6 

Yes. there is a constant ratio of number of calories to gram of protein.12/3=24/4=32/8=44/11=4