Answer:
r = 6
Explanation:
Calculate the slope m using the slope formula and equate to

m =
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with (x₁, y₁ ) = ( 3, - 6) and (x₂, y₂ ) = (11, r)
m =
=
=
( cross- multiply )
2(r + 6) = 24 ( divide both sides by 2 )
r + 6 = 12 ( subtract 6 from both sides )
r = 6