Çözüldü Composite Functions - Single Variable Equations - Inverse Functions

f(x) = 2x + 5. For what value does f(f(f(x))) = 10?

A) -3.625
B) -3.5
C) -3.375
D) -3.25
E) -3.125

https://perfectmathsat.com/extremely-challenging-sat-math-level-2-questions/#
(The Last Question)

2·[ 2·(2x + 5) + 5 ] + 5 = 10
2·[ 2·(2x + 5) + 5 ] = 5
4·(2x + 5) + 10 = 5
4·(2x + 5) = -5
8x + 20 = -5
8x = -25
x = -25 / 8 = -3.125 .

Solution - 2:
f(x) - 5 = 2x
[ f(x) - 5 ] / 2 = x
(x - 5) / 2 = f^(-1) (x)

f^(-1) o (f o f o f) (x) = f^(-1) (10)
(f o f) (x) = (10 - 5) / 2 = 5 / 2
f^(-1) o (f o f) (x) = f^(-1) (5 / 2)
f(x) = (5 / 2 - 5) / 2 = -5 / 4
(f^(-1) o f) (x) = f^(-1) (-5 / 4) = (-5 / 4 - 5) / 2 = -25 / 8 = -3.125 .