To find the value of \( b \) (the vertical intercept), we need the equation of the line in the form \( y = mx + b \), where \( m \) is the slope and \( b \) is the y-intercept.
From the points given, we can find the slope \( m \) using the two points \( (1,5) \) and \( (3,8) \):
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Find the slope \( m \): \[ m = \frac{y_2 - y_1}{x_2 - x_1} = \frac{8 - 5}{3 - 1} = \frac{3}{2} = 1.5 \]
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Now, we will use one of the points to solve for \( b \). Let's use the point \( (1, 5) \): \[ y = mx + b \] Plugging in the values, we have: \[ 5 = 1.5(1) + b \] \[ 5 = 1.5 + b \] Now, solve for \( b \): \[ b = 5 - 1.5 = 3.5 \]
Thus, the value of \( b \) (the vertical intercept) is: \[ \boxed{3.5} \]