Sarah has completed 0.4 of her word puzzle book, which contains 90 puzzles. If she completes 6 more, how many puzzles are left to complete?

Answer: 48.

Step 1: multiple 90 puzzles x 0.4 to find how many she has already completed = 36.

Step 2: subtract the number completed (36) from the total (90). 90-36 = 54

Step 3: subtract the 6 more she will complete. 54-6 = 48