It can be calculated this way:
As can be seen on the picture, there’re three mole of green (P1)
P1 = 0.63 atm = 2*3 atoms
P2 = 5 moles of diatomic orange
P3 = 6 moles of diatomic blue
P (total) = P1 + P2 + P3
P (total) = 0.63 + 0.63*5/6 + 0.63
P (total) = 1.79 atm