Short answer: 39
y = 7x - 3
f(x) = y = 7x - 3 Though there are some slight differences between f(x) and y, it is safe to say that f(x) acts (in this case) as a y value. So the question now is what does y(6) mean?
y(6) means exactly the same thing as what f(6) would mean. The both mean that where ever you see an x, put in a 6.
So y(6) means 7x - 3 = 7*6 - 3 = 39
