Answer : Option A
Explanation:
we can clearly see that from x+ y=5 we can substitute y = 5-x in y = 9x^2
Option B is clearly incorrect x can not be y -5
Option C is incorrect because y can not be 5 +x
Option D is incorrect because its y = 9x^2 not y^2 =9x^2 so y can not be 3x
if its y^2 = 9x^2 then only implies y = 3x
7/3x+1/3x=3x+6/3+5/3x
8/3x-5/3x=3x+6/3
3/3x=3x+6/3
x=3x+6/3
x-3x=6/3
-2x=2
-x=2/2
-x=1
x=-1