In the diagram below , what is the value of a?

Step-by-step explanation:
solution
let,
AB = 9
AC = 9 + 3a - 6
AD = 12
AE = 12 + 20
now
AB/AD = AC/AE
or, 9/12 = 3 + 3a / 22
by cross multiply
or, 9×22 = 12×(3 + 3a)
or, 198 = 36 + 36a
or, (198 - 36)/36 = a
or, 4.5 = a