please help.

answers:

a.A(–12, –7), B(8, –2), C(0, 7)

b.A(–6, –7), B(4, –2), C(0, 7)

c.A(–3, –3.5), B(2, –1), C(0, 3.5)

d.A(–12, –14), B(8, –4), C(0, 14)