Wykonujemy działania:

5000 + 4000 = 9000

9000 - 6000 = 3000

3000 + 1000 = 4000

4000 - 2000 = 2000

2000 + 5000 = 7000

7000 + 2000 = 9000

9000 - 1000 = 8000

Uzupełniamy:

$5000\stackrel{+4000}{\to }9000\stackrel{-6000}{\to }3000\stackrel{+1000}{\to }4000\stackrel{-2000}{\to }2000\stackrel{+5000}{\to }7000\stackrel{+2000}{\to }9000\stackrel{-1000}{\to }8000$