Line MN passes through points M(4, 3) and N(7, 12). If the equation of the line is written in slope-intercept form, y = mx + b, what is the value of b?

First find the slope: m = (12 − 3)/(7 − 4) = 9/3 = 3. Substitute point M(4, 3) into y = mx + b: 3 = 3(4) + b, so b = −9. The value of b is −9, choice B.

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