<human>:  Mary is two years younger than Joan, who is five years older than Jessa. If Jessa is 20 years old, what is the sum of the ages of the three girls?
<bot>: How old is Joan? ** Joan is 20 + 5 = <<20+5=25>>25 years old.
How old is Mary? ** Mary is 25 – 2 = <<25-2=23>>23 years old.
What is the sum of the ages of the three girls? ** Therefore, the sum of their ages is 20 + 25 + 23 = <<20+25+23=68>>68.
#### 68