Question

In two inequalities below,both a and b are integers.how many values do a and b have in common?


4< a < 21 12< b < 24
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a can be 5, 6, .. 19 or 20
b can be 13, 14, ...22 or 23.

Both a or b can be integers 13 through 20. Those are the "values in common" to both sets.