A functional relationship will have only one value of dependent variable for each value of independent variable. That is, the column on the left can only have one arrow tail per item.
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a) is a function. Each independent variable maps to one dependent value
b) not a function. Independent variable values 7 and 30 map to two values each.
About 2884 people practice a sport/club 1133 people nap 618 people work 1751 people do homework 1442 people play games 1339 people eat a snack 1133 people are on social media ...after school
