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common sence
100

15 + b = 28

b=13

100

44*1-c=42

c=2

100

2*2+K=10

K=6

100

28-4+Z=27

 Z=3

100

2+2=a

a=4

200

2,000+4+900+50+c=4,354

c=1,400

200

163*11-S=1693

S=100

200

2*4+S=107

S=99

200

21+2-R=22

R=1

200

3*3=r

r=9

300

50,000+40,000+Y+20+600+100=90,722

Y=2

300

144*50-Q=1148

Q=52

300

9*9+G=86

G=5

300

22+23-d=40

d=5

300

9*9=w

w=81

400

100,000+20,000+3,000+951+N+82+7=124,040

N=0

400

2,000*252-L=502,000

L=2,00

400

5*5+T=85

T=60

400

40+22-f=22

f=40

400

8*9=t

 t=72

500

124,040+A+40+24,040=170,320

A=22,2222

500

240*22-P=5140

P=140

500

96*2+U=230

U=38

500

49+78-w=107

w=20

500

12*12=u

u=144