The number of 9 more than 80% of a number is 14.6. Find this number (by solving the equation)

The number of 9 more than 80% of a number is 14.6. Find this number (by solving the equation)

Let this number be X
X*80%+9=14.6
0.8X=14.6-9
0.8X=5.6
X=5.6/0.8
X=7

7x+8=5x+15

7x+8=5x+15
2x=15-8
2x=7
x=7/2

A simple solution to an equation
It is known that f (x) = 2x-1,
Find the solution of the equation f (f (f (f (x)))) = 1
Is there a simple solution to this equation?
What if f (f (f (x))) = 3?

Push backwards:
f(f(f(f(x))))=1
f(f(f(x)))=(1+1)/2=1
f(f(x))=(1+1)/2=1
f(x)=(1+1)/2=1
x=(1+1)/2=1

Solving a simple equation
The unknown number is X. please list the calculation process in detail,
X/15000+X=13%
I am not good at mathematics

X=0.13(15000+X)
X=1950+0.13X
X(1-0.13)=1950
0.87X=1950
X=1950÷0.87
X≈2241.4