Answer:
$120
Step-by-step explanation:
Zero pair is a pair of numbers whose sum is zero, e.g. +5, -5. Assigning a negative value to expenditures, Ingrid spent money represents $-120. From the definition, it is deduced that $120 make the zero pair in this case. So, she must earn $120.
help
a
the number of common customers are 8 in number
