Diketahui fungsi f = 2 -3. tentukan nilai a Jika a = -18

Jika soal ↓
f(x) = 2x - 3

f(a) = 2(a) - 3
-18 = 2a - 3
2a = -18 + 3
2a = -15
a = -15 : 2
a = -7,5

Jika soal ↓
f(x) = 2 - 3x

f(a) = 2 - 3(a)
-18 = 2 - 3a
3a = 2 + 18
3a = 20
a = 20 : 3
a = 6,67

Semoga berguna +_+