Suppose that we are told that four number

a, b, c, d

lie between

- 5

and

5

Suppose also that the numbers are constrained so that $5 < a + b < 10$ and $- 10 < c + d < - 5$

Given this information, what can you deduce about these inequalities?

$? ? < a + b - c - d < ? ?$

$? ? < a + c < ? ?$

$? ? < a - c < ? ?$

$? ? < a - c + d - b < ? ?$