bantu jawab..tolong jawab pertanyaan ini..terimakasi

Materi : Nilai Mutlak
Bahasan : Persamaan Nilai Mutlak
Jawaban : x = - 40 atau x = 60

Langkah - langkah :
|f(x)| = a, ⇒ f(x) = a atau f(x) = - a
|4 - (2/5)x| - 7 = 13
|4 - (2/5)x| = 13 + 7
|4 - (2/5)x| = 20

⇒ 4 - (2/5)x = 20
20 - 2x = 100
- 2x = 100 - 20
- 2x = 80
- x = 40
x = - 40

⇒ 4 - (2/5)x = - 20
20 - 2x = - 100
- 2x = - 100 - 20
- 2x = - 120
x = 60