Step-by-step explanation:
hope I understand your qyestion
Equation 1 : R+G=20
Equation 2 : 7R+3G=9
Multiply Equation by 3, it becomes
3R+3G=60 ...... Equation 3
Now Equation 3 minus Equation 2
-4R = 51
R = - 51/4
Sub R into Equation 1, you can find G
