Given that $(3,15)$ is on the graph of $y = f(x)$, find a point that must be on the graph of $y = f(x) - 7$. Express your answer as an order

Given that $(3,15)$ is on the graph of $y = f(x)$, find a point that must be on the graph of $y = f(x) - 7$. Express your answer as an ordered pair $(a,b)$ where $a$ and $b$ are real numbers.