(3,4) and (-5,6) are "coordinate planes".
These appear in algebra and math when you're graphing. These coordinate planes consist of "x" and "y" (x,y). The x's (which are 3 and -5 in your situation) should be graphed accordingly using the x-axis and the y's (which are 4 and 6 in your situation) should be graph accordingly using the y-axis.
Answer is A.
rate = 10/1 = 10ft and passing origin (0,0)
<span>a=7b+8c+9d-10
a = 8c + 16d - 10
solve for c then
8c = a - 16d + 10
c = (</span>a - 16d + 10) / 8
or
c = a/8 - 2d + 5/4
