Show:
P
Q
R
100

450 x 2000

900 000

100

840 000 / 400

2100

100

100 - 20 x 4 + 5

25

200

(60 + 40 ) / (25 / 5) 

20

200

12 x (15 - 5) / 4

30

200

48 / 6 x 2

16

300

5 x 5 / 5 x 5

25

300

15 + 45 / 5 x 3

42

300

500 - (10 x 4 + 60 / 3)

440

400

_____ x 2 - 8 = 10

What is the missing number 

9

400

________ / 2 + 400 = 3000

5200

400

_______ - 3 x 2 = 100

53