Question

Does anyone know the answer?

Answer 1

Answer:

d = 9

Step-by-step explanation:

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

m = $\frac{y_{2}-y_{1} }{x_{2}-x_{1} }$

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

m = $\frac{21-6}{d-4}$ , that is

$\frac{15}{d-4}$ = 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