To find the equation representing the proportional relationship between the cost of deli meat and its weight, we start by representing the cost as \(y\) and the weight in pounds as \(x\).
Given that Nigel paid $10 for 2 pounds of roast beef, we can express this relationship as:
\[ y = kx \]
where \(k\) is the constant of proportionality (the cost per pound).
To find \(k\), we use the given information:
\[ 10 = k \cdot 2 \]
Solving for \(k\):
\[ k = \frac{10}{2} = 5 \]
Now we can write the equation that represents the cost of the roast beef:
\[ y = 5x \]
Thus, the equation for the graph of this proportional relationship is:
\[ y = 5x \]