Ok so f(x) basically means the same thing as the variable y (if you were to graph).
f(x)
Is basically saying if x is whatever (in this case 7.6), then f(x) is whatever the y value would be. When it states f(7.6), it is basically saying that x=7.6.
So now that we understand that x=7.6, we can substitute the value of x into the equation.
f(7.6)=(1/2)*(7.6)
f(7.6)=(1/2)*(3/5+35/5)
f(7.6)=(1/2)*(38/5)
f(7.6)=38/5
I hope that made sense! Good luck!