Answer:
900<x<1100
Step-by-step explanation:
The third side must be greater than the difference of the other two sides
10000- 1000 < 10x
9000< 10x
Divide by 10
9000/10 < x
900 < x
The third side must be smaller than the sum of the other two sides
10000+1000 > 10x
11000>10x
Divide by 10
11000/10>10x/10
1100>x
900<x<1100
