For the reaction, A → B as it follows second order kinetics, therefore the rate law equation will be
Rate = k[A]2 = kx2
if [A] = x mol-1
if the concentration of A is increased three times, then
[A] = 3x mol L-1
∴ Rate = k (3x)2 = 9 kx2
Thus, the rate of the reaction will become 9 times.
Hence the rate of formation of B will increase by 9 times.