human
Twice Betty's age is the cost of a pack of nuts. Doug, Betty's friend, is 40 years old. If the sum of their ages is 90, and Betty wants to buy 20 packs of the nuts, calculate the amount of money she'll pay for the packs of nuts.
assistant
How old is Betty? ** If Doug, Betty's friend, is 40 years old, and the sum of their ages is 90, Betty is 90-40 = <<90-40=50>>50 years old.
How much does a pack of nuts cost? ** Since twice Betty's age is the cost of a pack of nuts, a pack of nuts is sold at 2*$50 = $<<2*50=100>>100
How much money will Betty pay for the packs of nuts? ** If Betty wants to buy 20 packs of the nuts, she'll have to pay 20*$100 = $<<20*100=2000>>2000
#### 2000