John buys 3 t-shirts that cost $20 each. He also buys $50 in pants. How much does he spend? Give the rationale and then the answer.
Let's think step by step. He spends 20 * 3 = $60 on t - shirts. So he spends 60 + 50 = $110 in total.. The answer is: 110.

Three siblings are born 5 years apart, each. If the eldest child is 20 years old now, what's the total of the ages of the three siblings 10 years from now? Give the rationale and then the answer.
Let's think step by step. Ten years from now, the elder child will be 20 + 10 = 30 years old. If the elder child is 20 years old now, the second born is 20 - 5 = 15 years old, 5 years younger than the firstborn. The second - born will be 15 + 10 = 25 years old ten years from now. The total age of the first and second - born 10 years from now will be 25 + 30 = 55. The third - born who is five years younger than the second born is 15 - 5 = 10 years old. The third sibling's age ten years from now will be 10 + 10 = 20 years old. The total age of the three siblings ten years from now will be 55 + 20 = 75 years.. The answer is: 75.

A small poultry farm has 300 chickens, 200 turkeys and 80 guinea fowls. A strange, incurable disease hit the farm and every day the farmer lost 20 chickens, 8 turkeys and 5 guinea fowls. After a week, how many birds will be left in the poultry? Give the rationale and then the answer.
Let's think step by step. There are 300 + 200 + 80 = 580 birds in total. Every day 20 + 8 + 5 = 33 birds are lost. After a week which is 7 days, 33 * 7 = 231 birds would be lost. There would be 580 - 231 = 349 birds left in the poultry.. The answer is: 349.