Answer: 3000 stamps
Step-by-step explanation:
Given
Chris and Josh have 1800 stamps
Josh and Jessica have 2200 stamps
Jessica and Chris have 2000 stamps
Suppose Chris, Josh, and Jessica have [tex]x,y, \text{and}\ z[/tex] stamps
[tex]\therefore x+y=1800\quad \ldots(i)\\\Rightarrow y+z=2200\quad \ldots(ii)\\\Rightarrow z+x=2000\quad \ldots(iii)\\\text{Add (i), (ii), and (iii)}\\\Rightarrow 2(x+y+z)=1800+2200+2000\\\Rightarrow x+y+z=3000[/tex]
Thus, all three have 3000 stamps
