So we know that f of seven, so when x is equal to seven, we're going to, this expression is going to evaluate to this thing, 40 plus 5e to the seven. So five times e to the seventh power plus c is equal to 40, is equal to 40 plus 5e to the seventh power. And notice all I did is said okay, f of seven. 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.