The domain of a relation is

the output (y) values of the relation
the input (x) values of the relation
a set of points that pair input values with output values
x and y values written in the form (x, y)

the input (x) values of the relation

Step-by-step explanation:

(a) No, The output (y) values of the relation are called Range. So it is the wrong option.

(b) Yes, the input (x) values of the relation are called Domain. Thus, it is the correct option.

(c) No, it is not a definition of Domain. Thus, this is an incorrect option.

(d) No, it is not a definition of Domain. It is called the cartesian point. Thus it is also an incorrect option.

Further,

The Domain is the all possible input values of a function that gives defined values.  

The Range is the all defined output values that we get from a function (or y).

21

step-by-step explanation:

answer set (b) 0.5, 3/4 80% is in order from least to greatest.  

step-by-step explanation:

in order to compare rational numbers to each other, it is much easier if they are in the same form.   typically, the best form in which to evaluate rational numbers is in decimals.   in order to convert a percent to a decimal, you would divide the given percentage by 100.   you can also accomplish the conversion by moving the decimal point over two places to the left.   for example, the decimal value of 80% is 80/100, or 0.8.   in order to convert a fraction to a decimal, you need to divide the numerator by the denominator.   for example, 3/4 is 0.75.   so, for choice (b) 0.5 3/4 (0.75), 80% (0.8) is the only choice in which the numbers are in order from least to greatest.