Hi there
The answer to your question is
x=2y+8
Well, first off, let's find what is the slope of BC

now, a line perpendicular to that one, will have a negative reciprocal slope, thus

now, we know the slope "m" of AB is -2 then, thus
C= 5.5 I'm pretty sure that's the answer
d= 4.5 and c+ 5.5
Because 4.5 plus 1.0 = 5.5
since c is one more than d
5.5 plus 4.5 = 10