ANSWER and EXPLANATION
The equation that represents the situation is:
[tex]\begin{gathered} D=7L \\ \text{where D = amount he earns} \\ L=\text{ number of lawns mowed} \end{gathered}[/tex]
To fill the table, substitute the value of L and find the corresponding value of D and vice versa:
[tex]\begin{gathered} \text{when L = 1:} \\ D=7\cdot1 \\ D=\text{ \$7} \end{gathered}[/tex][tex]\begin{gathered} \text{when D = 21:} \\ 21=7\cdot L \\ L=\frac{21}{7} \\ L=3\text{ lawns} \end{gathered}[/tex][tex]\begin{gathered} \text{when L = 4:} \\ D=7\cdot4 \\ D=\text{ \$28} \end{gathered}[/tex]
Now, plot the graph:
