We have a question: Mike wants to buy a new phone. The cost of the phone is $1300. How much more money does Mike need if he already has 40% of the amount he needs?
And an answer: 780
So how you got the answer?
Mike already has 40 / 100 * 1300 = $520. This means he needs 1300 - 520 = $780 more, to buy the phone.

We have a question: Jerry bought 48 firecrackers for the 4th of July. A police officer discovered and confiscated 12 of them. 1/6 of the remaining ones were defective. If Jerry set off half the good firecrackers, how many firecrackers did he set off?
And an answer: 15
So how you got the answer?
First subtract the 12 confiscated firecrackers from the original number: 48 firecrackers - 12 firecrackers = 36 firecrackers. Then multiply this number by 1 / 6 to find how many were defective: 36 firecrackers * 1 / 6 = 6 firecrackers. Then subtract the defective firecrackers to find how many were good: 36 firecrackers - 6 firecrackers = 30 firecrackers. Then divide this number in half to find how many firecrackers Jerry set off: 30 firecrackers / 2 = 15 firecrackers.

We have a question: Jose is a collector of fine wines. His private cellar currently holds 2400 bottles of imported wine and half as many bottles of domestic wine as imported wine. If Jose holds a party and the guests drink one-third of all his wine, how many bottles will remain in his cellar?
And an answer: 2400
So how you got the answer?
Jose has half as many bottles of domestic wine as imported wine, or 2400 / 2 = 1200 bottles of domestic wine. In total, he has 2400 + 1200 = 3600 bottles of wine. If the guests drink one - third of all his wine, then they will have consumed 3600 / 3 = 1200 bottles of wine. Thus, after the party, Jose's private cellar will have 3600 - 1200 = 2400 remaining bottles of wine.