Answer:
a = 4.2
Step-by-step explanation:
Given that,
f(x) = 5x-4 ...(1)
f(4a) = 80
We need to find the value of a.
Put x = 4a in equation (1) and equate with 80. So,
5(4a)-4=80
Adding 4 both sides,
20a-4+4=80+4
20a=84
⇒ a = 4.2
So, the value of a is 4.2. Hence, the correct option is (a).
