VECTORS PROBLEM! PLEASE HELP!

AB = a + tb and CD = a + (3t – 5)b where t is a number.
Find the value of t when AB = CD .

I need a step by step answer please.
Thanks!

if AB = CD

then

a + tb = a + (3t - 5)b

→ tb = (3t - 5)b

→ t = (3t - 5)

→ -2t = -5

→ t = 5/2