The correct option is B 12
[Beware of option D we need to check whether given values satisfy the system ]
We should first substitute (1, 1) in to the second equation to see it (1, 1) is a possible solution
p=2q−1
1=2(1)−1
1 = 1
Because the second equation created a true statement, we proceed by substituting (1, 1) into the first equation.
2a(2(1)−1)=1
2a(2−1)=1
2a=1
a=12