Answer:
75
Explanation:
f(4) means to use 4 in place of x.
f(x) = 3(5)^(x-2)
fill in 4 for
f(4) = 3(5)^(4-2)
do the 4-2 subtraction first
f(4) = 3(5)^2
do the 5 to the 2nd power next.
f(4) = 3(25)
last, multiply.
f(4) = 75
This is just following the typical order of operations.