I bought 3 Books my total is 150$ 1 book is 50% more expensive than all of them how much is it

The more expensive book cost $90, the other two combined cost $60.

Step-by-step explanation:

x = cost of more expensive book

y = subtotal cost of the other books

x = 50% more than y, so x = 1.50y = 1.5y

x + y = total cost = $150

1.5y + y = 150

y = 150/2.5 = 60

x = 1.5y = 1.5 (60) = 90