Hey there! I'm happy to help!
Our goal here is to write the function (equation) that represents what Carlos has graphed. This is a line, so we can use the slope-intercept equation to represent it.
Our slope-intercept equation is y=mx+b, where m is the slope and b is the y-intercept.
If we look at the graph, we see that the the line intersects the y-axis at the point (0,0), also known as the origin, so our y-intercept is 0.
To find our slope, we need to first find two points on the line. Well, we already have (0,0). The next point on the line that seems to have integers is (7,5). This means that from (0,0) our rise is 5 and our run is 7, and since slope is rise over run, that means that our slope is 5/7 (for every one unit we go over, the line goes up 5/7).
Now, we just throw these numbers into the equation.
y=5/7x
or
f(x)=5/7x (if it needs to be in that function format)
Have a wonderful day and keep on learning! :D