Question 1054097
Presumably, one wants the point-slope formula
y-y1=m(x-x1)
For the first
y-(-50)=-3(x-15)
y+50=-3x+45
y=-3x-5; -50=-45-5, check
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y=0.5(x-28)
y=(1/2)x-14; 28(1/2)-14=0, check