Well if this is f of x, f of, let me write this down. So if this is f of seven, if this is f of x, I just replaced the x with a seven to find f of seven, and we know that f of seven is also going to be equal to that, they gave us that information. But when you just look at this, it's pretty easy to figure out what c is going to be. You can subtract 5e to the seventh from both sides, and you see that c is equal to 40. And so we can rewrite f of x, we can say that f of x is equal to 5e to the x plus c, which is 40. And so now from that, we can evaluate f of zero. F of zero is going to be five times e to the zero power plus 40, e to the zero is one, so it's going to be five times one, which is just five, plus 40, which is equal to 45, and we're done.