Answer: 100%
Step-by-step explanation
Let the number be 100
Add 25% to it :- 100+25% of 100 i.e., 100+25= 125
Subtract 20% of the resultant from it :- 125-20% of 125 i.e., 125-25= 100
The answer is 100%
F(4) = 7+4(4-1)
f(4) = 7+4(3)
f(4) = 7+12
f(4) = 19
The forth term is 19
f(40) = 7+4(40-1)
f(40) = 7+4(39)
f(40) = 7+156
f(40) = 163
The fortieth term is 163
There are an infinite number of possibilities, and not enough information
to decide which possibility is really the one inside the function machine.
Here are a few. Each of these gives the result that you described,
and there are an infinite number of others:
f(x) = x
f(x) = 2x + 1
f(x) = 10x + 9
f(x) = x² - 2
f(x) = 7x² - 8
f(x) = 31x³ + 30
f(x) = log( |x| ) - 1
f(x) = ln( |x| ) - 1
f(x) = x tan(45°)
.
.
etc.
5*sqr(2) is the right answer