Question

Does anyone know the answer?

Answer 1

d = 9

Explanation:

Calculate the slope m using the slope formula and equate to 3

m =
`(y_(2)-y_(1) )/(x_(2)-x_(1) )`

with (x₁, y₁ ) = (4, 6) and (x₂, y₂ ) = (d, 21)

m =
`(21-6)/(d-4)` , that is

`(15)/(d-4)` = 3 ← multiply both sides by d - 4

15 = 3(d - 4)

15 = 3d - 12 ( add 12 to both sides )

27 = 3d ( divide both sides by 3 )

9 = d , that is

d = 9