The answer is d. The reason this is the answer is because to find the area of a triangle you will find half of the base times the height. The formula looks like this: A=1/2bh.
On this picture the base is the length of the bottom part of the triangle (c). It is the distance of the solid line only.
The height is represented as the straight line that is perpendicular to the base (forms a right/90 degree angle). X is the height of the triangle.
Therefore, 1/2cx is the answer.
You could maybe think about the numbers like fractions,decimals and never ending numbers.
3/10 is the same as 15 out of 50. subtract 15 from 50 and you get 35, the answer.
A correlation coefficient shows how linear a set of data is, so for any points that comply with the given equation, the correlation coefficient will be one, that is, the correlation is completely linear, because the given equation is alinear one, there is a linear correlation of x and y. Indeed, the equation is a line equation in general form.