The following is a double inequality.
-9 <5 ≤ 6
In a double inequality we are saying that both of the inequalities have to be simultaneously true. In this case 5 it is definitely greater than -9 and at the similar time is less than or equal to 6. Thus, this double inequality is a true inequality.
Conversely, 10 ≤ 5 < 20 is not a true inequality. Whereas this is true that 5 is less than 20 (so the second inequality is true) this is not true that 5 is greater than or equal to 10 (thus the first inequality is not true). If even one of the inequalities into a double inequality is not true then the whole inequality is not true. This point is more significant than you may realize at this point. In a later section we will run across condition where several students try to combine two inequalities in a double inequality which simply can't be combined, so be careful.