the general form of the equation is
[tex]y=mx+b[/tex]where m is the slope and b the y-intercept
from the graph we can notice the y-intercept is 0 because touch the y-axis on 0, so b=0
now we can repalce a point and b on the general equation to find the slope, m
i will use the point ( 90 , 30 )
so
[tex]\begin{gathered} (30)=m(90)+0 \\ 30=90m \\ m=\frac{30}{90} \\ \\ m=\frac{1}{3} \end{gathered}[/tex]the slope is 1/3
so the equation is
[tex]y=\frac{1}{3}x[/tex]