Brainliest reward if you get this right plus 20 points

The equation of the relation ⇒

y = 18

Step-by-step explanation:

∵ y ∝ x/z

∴ y = kx/z

∵ y = 18 , x = 15 and z = 5

∴ 18 = 15k/5 ⇒ 18 = 3k

∴ k = 18/3 = 6

∴ y = 6x/z

∵ x = 21 and z = 7

∴ y = (6 × 21)/7 = 18

d

step-by-step explanation:

none of the above.

for one of the equations to be used in the process, there has to be a term in the equation since squared is .

since there is only a term in the first equation, we cannot derive a from completing the square.

solving with completing the square