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 :-)