Question: There are 50 marbles in a box which has a mixture of white, red and blue marbles. There were originally 20 white marbles and an equal number of red and blue marbles. Jack removes a number of marbles equal to double the difference between the number of white marbles and the number of blue marbles. How many marbles are left in the box?
Answer with step-by-step thinking: 20 of 50 marbles are white so there are 50 - 20 = 30 red and blue marbles. The number of red marbles and blue marbles is the same, so there are 30 / 2 = 15 of each color. The difference between the number of white marbles and blue marbles is 20 - 15 = 5. Double the difference is 5 * 2 = 10 marbles. 10 marbles are removed to leave 50 - 10 = 40 marbles.
So the answer is 40.

Question: Miranda wants to buy a pair of heels she saw online. She saved money for 3 months. Her sister heard that she was sad and gave her $50 for her to buy the heels. If she paid $260 in total for the heels, how much money did she save per month?
Answer with step-by-step thinking: First find the total amount of money she saved: $260 - $50 = $210. Then divide that number by the number of months she saved to find the amount she saved each month: $210 / 3 months = $70 / month.
So the answer is 70.

Question: Chester must deliver ten bales of hay to Farmer Brown. Farmer Brown wants Chester to supply better quality hay and double the delivery of bales of hay. If the previous hay cost $15 per bale, and the better quality one cost $18 per bale, how much more money will Farmer Brown need to meet his own new requirements?
Answer with step-by-step thinking:
The hay previously cost $15 per bale so 10 bales would cost $15 * 10 = $150. Double 10 bales is 10 * 2 = 20 bales. Better quality hay cost $18 per bale so 20 bales would cost $18 * 20 = $360. Farmer Brown would need $360 - $150 = $210 more.
So the answer is 210.