All you gotta do is pick a random point on the x-axis, lets say, x=2 in this case, and plug it into the equation.
If x=2, y = (1/2)2 - 3 = 2 - 3 = -1
When x = 2, y = -1
Now pick another point, x = 1
x = 1, y = (1/2)1 - 3 = 0.5 - 3 = - 2.5
When x = 1, y = - 2.5
Draw a cross on those 2 points, on the 2d plane
(1, -2.5) and (2, -1)
and draw a line between them, and make the line continue past the points, having no boundaries but the paper you hold, keeping it straight the entire time. With not turns.
If you want to draw out a table, make it have 2 rows, and 6 columns.
Write x in the first column of the first row, and write y in the first column of the second row.
Now, write down a different, random x value, in each column in the first row.
In the second row, in each column, write the y value, that corresponds to the x value given above each individual column, based on the equation
y = 1/2x - 3.
The resultant velocity of the plane is the sum of the two velocity vectors which are perpendicular to each other. See the attached figure.
The magnitude of the resultant velocity is
.
The approximate value of the actual velocity of the plane is 
. Correct choice is (D).
Ratio of cat : to dog = 40 : 20 = 2:1
X=14
Y=15
Im assuming you want to find out what x and y are
