diketahui suatu fungsi f(5a + 2 ) = 20a + 5 nilai fungsi f(3) adalah.. pake cara okee

Misalkan 5a+2=x
a= (x-2)/5
f(a) = 20((x-2)/5)+5
f(a)= 4x-3
F(3) = 12-3=9

f(5a + 2) = 20a + 5
f(3) = ?

cari dulu a nya
3 = 5a + 2
3-2 = 5a
1 = 5a
a = 1/5

f(3) = f(5a + 2) = 20a + 5
f((5 × 1/5) + 2) = (20 × 1/5) + 5
f(3) = 4 + 5
f(3) = 9

semoga membantu ^^