1. The problem asks how to define the function $f(x,y)$ at the point $(7, y)$ or specifically at $x=7$. 2. Generally, a function of two variables $f(x,y)$ is defined by an expression or rule that assigns a value to each pair $(x,y)$ in its domain. 3. To define $f(7,y)$, you substitute $x=7$ into the function's formula, resulting in a function of $y$ alone: $f(7,y) = \text{expression with } x=7$. 4. For example, if $f(x,y) = x^2 + y^2$, then $f(7,y) = 7^2 + y^2 = 49 + y^2$. 5. Without a specific formula for $f(x,y)$, the general approach is to plug in $x=7$ into the given formula to get $f(7,y)$. 6. If the function is defined piecewise or has special conditions at $x=7$, those must be considered. 7. In summary, defining $fxy$ at $x=7$ means evaluating or expressing the function with $x$ fixed at 7, resulting in a function of $y$ only.