Answer:
x=-3/19
y=39/19
Step-by-step explanation:
the equations can be written as the following system

If the second equation is multiplied by 3/2 it will become -18x+3y=9
If that equation is then subtracted with the first you will obtain the following
-19x=3, it means x=-3/19
The other variable is obtained by substituting the new value for x in the first equationx+3y=6, thus we obtain that y=39/19
Answer:
Given that,
R = 3x + 9y
Also, given that,
y = 6
R = 7
We have to find the value of x
For that, you can to put 6 and 7 to the equation instead of y and R respectively.
R = 3x + 9y
7 = 3x + 9 × 6
7 = 3x + 54
7 - 54 = 3x
- 47 = 3x

Hope this helps you :-)
Let me know if you have any other questions :-)
1 gallon (it’s stayed in the question)
C should be your answer:))))