M(-12, 5)
P(9, -12)
Let:
N (xp, yp )
ratio a:b
xp = x1 + a/(a+b) (x2-x1)
yp = y1 + a/(a+b) (y2-y1)
Where:
x1 = -12
x2 = 9
y1 = -5
y2 = -12
a = 3
b= 4
Replacing the values:
xp = -12 + 3/(3+4) (9- (-12)) = -12 + 3/7 (21) = -3
yp = -5 + 3/(3+4) (-12 - (-5)) = -5 + 3/7 (-7) = -8
The coordinates of N are:
N = (-3,-8 )