Answer:
slope = 40
Step-by-step explanation:
Calculate the slope m using the slope formula
m = 
with (x₁, y₁ ) = (2, 80) and (x₂, y₂ ) = (4, 160) ← 2 points on the line
m =
=
=
= 40
A = Anthony's weight
B = Anthony's brother's weight
A = 2B + 9 Plug in Anthony's weight
59 = 2B + 9 Subtract 9 from both sides
50 = 2B DIvide both sides by B
25 = B Switch the sides to make it easier to read
B = 25
Anthony's brother weighs 25 pounds.