They are variables. They stand in for different numbers in a problem. for example) a=12
a x a x c = 3.9 * 3.9 * 3 =45.6345.63 * 2 = 91.26a x b x c = 3.9 * 5.7 * 3 = 66.6966.69 + 91.26 = 157.95 cubic units
That would be 4 thousands
The domain is the set of all first elements of ordered pairs (x-coordinates).
area = l x w
area = 9 x 9
area = 81
Hope this was helpful. :-)
