alguien me ayuda porfa con solución plis

1) AB = 3BC
BC = x
AB = 3x
x + 3x = 24
4x = 24
x = 6
BC = 6
2) AB/2 = BC/5 = 3
AB = 2 × 3 = 6
BC = 5 × 3 = 15
AC = 6 + 15
AC = 21