$$Yellow\ Phalaenopsises=P_y$$
$$white\ Phalaenopsises=P_w$$
$$white\ Gongoras=G_w$$
For the two orchid plants we have four different varieties of flowers.
Total orchid plants=54
$$P_y+P_w+G_y+G_w=54$$
How many of them are phalaenopsises? $$Find\ P_y+P_w$$

Statement1 : Ross grows 14 Phalaenopsises that have white colour
$$P_w=14$$
$$P_y+14+G_y+G_w=54$$
$$P_y+G_y+G_w=54-14$$ ; statement 1 is INSUFFICIENT

Statement 2: Total number of Gongoras is 50% greater than the number of yellow Phalaenopsises.
$$G_y+G_w=\ 150\%\ of\ P_y$$
$$\ P_y+P_w+\left(\frac{3}{2}\left(P\right)_y\right)=54$$
Statement 2 is INSUFFICIENT

combining statement 1 and 2 together
P $$P_y+P_w+G_y+G_w=5$$
$$from\ statement\ 1,\ P_w=14\ \ \ from\ statement\ 2;\ \ G_w+G_y=\frac{3}{2}\left(P_y\right)$$
$$P_y+14+\left(\frac{3}{2}P_{y_{ }}\right)=54-14=40$$
$$P_y=\frac{40\cdot2}{4}=20$$ $$Total\ number\ of\ phalaenopsises=P_y+P_w=20+14=34\ $$
$$Two\ statements\ together\ are\ SUFFICIENT;\ option\ C$$