Question

if f(x)=9C/5+32. find 1)f(0) 2) f(28)​

Answer 1

I think there's something missing in this question,
So I'll be adding another line, x=C

We have the function as,

$f(x) = \frac{9C}{5} + 32$

So what you have to do while solving such questions is substitute for the value given for x in the function.
i.e for a function f(x) = 4x when you have to solve f(y) you simply just substitute y for x everywhere in that function making the one here as f(y) = 4y

Using the same logic

Now lets do it,

(i)
$f(0) = \frac{9(0)}{5} + 32 \\ \\ = 0 + 32 \\ \\ = 32$

(ii)

$f(28) = \frac{9(28)}{5} + 32 \\ \\ = \frac{252}{5} + 32 \\ \\ = 50.4 + 32 \\ \\ = 82.4$


Hope I was able to break it down for you.