Peggy has 6 dolls and her grandmother gave her 30 so that's 6 + 30 = 36 dolls. Over the holidays, Peggy is gifted half the number of dolls her grandmother gave her, so she receives 30 / 2 = 15 more dolls. Peggy had 36 dolls and received another 15 for a total of 36 + 15 = 51 dolls.
The answer: 51
Reverse engineering the question: Peggy has 6 dolls. Her grandmother gives Peggy her own collection of 30 dolls. Over the year, Peggy receives half that amount of dolls between her birthday and Christmas. How many dolls does Peggy now have?

There are thirty games in the season because 20 + 10 = 30. He needs to get 90 hits on the year to average 3 hits a game because 30 x 3 = 90. He has 40 hits already because 20 x 2 = 40. He needs 50 hits in the final 10 games because 90 - 40 = 50. He needs to average 5 hits a game because 50 / 10 = 5.
The answer: 5
Reverse engineering the question: Javier plays 2 baseball games a week. In each of his first 20 games, he averaged 2 hits. If he has 10 games left, how many hits a game does he have to average to bring his average for the season up to 3 hits a game?

Two aeroplanes require 240 legos / airplane x 2 airplanes = 480 legos. Julian needs 480 legos - 400 legos = 80 more legos.
The answer: 80
Reverse engineering the question: Julian has 400 legos and wants to make lego models of two identical airplanes. If each airplane model requires 240 legos, how many more legos does Julian need?

Maila read 12 x 2 = 24 pages today. So she was able to read a total of 12 + 24 = 36 pages since yesterday. There are 120 - 36 = 84 pages left to be read. Since she wants to read half of the remaining pages tomorrow, then she should read 84 / 2 = 42 pages.
The answer: 42
Reverse engineering the question:
Julie is reading a 120-page book. Yesterday, she was able to read 12 pages and today, she read twice as many pages as yesterday. If she wants to read half of the remaining pages tomorrow, how many pages should she read?