The "formula" to figure the new points is as follows :
New point = ( Vertex of triangle - Dilation Center)*Scale Factor + Dilation Center
So we have
[ ( -3 , 7) - ( 5, -5)] *14 + (5, -5) =
[ (-8, 12) ] *14 + ( 5, -5) =
(-112, 168) + (5, -5) =
(-107, 163)
[ ( -7 , -5) - ( 5, -5)] *14 + (5, -5) =
[ (-12, 0) ] *14 + (5, -5) =
(-168, 0) + (5, -5) =
(-163, -5)
[ ( 9 , 3 ) - ( 5, -5)] *14 + (5, -5) =
[ (4, 8) ] *14 + (5, -5) =
(56, 112) + (5, - 5) =
(61, 107 )
Here's the pre and post images :