Answer:
AB = 30 units.
Explanation:
Given that in a triangle ACE, B and D are mid points of AC and CE respectively.
By triangle theorem for mid points, we have
BD = 1/2 AE
Since AE is given as 60, we get BD =30
But BD also equals 3x (given)
So 3x=30 or x =10
Substitute in AC to get AC = 5x+10 = 5(10)+10 = 60
AB = 1/2 AC = 1/2 (60) = 30 units.