Suatu fungsi didefinisi dengan rumus f (x)=2x-7, jika f (c) = 1, maka nilai c adalah

f(x) = 2x- 7
f(c) = 2c - 7 = 1
= 2c = 1 + 7
= c = 8 / 2
= c = 4

So easy and simple...

F(c)= 2(c)-7 =1
2(c)=8
c = 8 : 2
c = 4