Answer:
c. 130
Step-by-step explanation:
Let call B the quantity of voters who voted yes for both propositions.
From the question we know that twice as many voters voted "yes" for R as for S, that can be written as the following equation:
R+B=2(S+B)
Where R is the number who voted "yes" for R but "no2 for S and S is the number who voted "yes" for S but "no" for R.
Replacing R by 750 and S by 310 and solving for B, we get:
750+B=2(310+B)
750+B=620+2B
2B-B=750-620
B=130
So, 130 voters voted yes for both propositions
