Please help geometry work coordinates

(a,a)

Step-by-step explanation:

Keep in mind that the vertical line represents the y axis and the horizontal line represents the x axis

We want to find the coordinates of C

We can do this by looking at the given coordinates and the axis..

We are given that B is at (0,a) and we are given that D is at (a,0)

Now looking at C, we can tell that C shares the same y value as B and the same x value as D

If B has a y value of a and D has an x value of a then C would have an x and y value of a

Hence C would be at (a,a)