ANSWER
[tex]y=-\frac{1}{2}x+35[/tex]EXPLANATION
From the given diagram;
For any straight line;
[tex]\begin{gathered} y=mx+c \\ m=gradient,c=y-intercept \end{gathered}[/tex]The slope of the straight line is;
[tex]\begin{gathered} m=\frac{\Delta y}{\Delta x} \\ m=-\frac{1}{2} \end{gathered}[/tex]The y-intercept is;
[tex]35[/tex]Hence, the equation of the straight line is;
[tex]y=-\frac{1}{2}x+35[/tex]