For x = 4, then it means 3 to the fourth power or 3 times 3 times 3 times 3 times 3. 3^4 = 81 and 8 times that is 648.
y(x) = 8 * 3^x where x = 4:
y(x) = 8 * 3^4 = 8 * 81
y(x) = 648
The Function Rule then being that for every value of x there is one and only one value of y. y is the dependent variable and x is the independent variable.
