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 < ??