Palo ya baithuti mo holong ya sekolo e ne e le 1000. Holo e ne e na le matseno a le 3 e bong A, B, le C ao gape a neng a dirisiwa jaaka ditsela tsa go tswa. Fa pokano e sena go fela, 30% ya baithuti ba ne ba tswa mo kagong ka tsela ya go tswa ya A, 3/5 ya ba ba setseng ba ne ba tswa ka tsela ya go tswa ya B, mme ba bangwe botlhe ba ne ba tswa ka tsela ya go tswa ya C, bala palo ya baithuti ba ba tswileng ka tsela ya go tswa ya C.

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?
Palo ya baithuti ba ba tswileng ka tsela ya go tswa ya A ke 30/100%1000 = 300 baithuti.
Palo ya baithuti ba ba sa dirisang tsela ya go tswa ya A ke 1000-300 = <<1000-300=700>>700
3/5 ya baithuti ba ne ba dirisa tsela ya go tswa ya B, palogotlhe ya 3/5*700 = <<3/5*700=420>>420 baithuti.
Fa 420 ya baithuti ba ba setseng ba ba sa dirisang tsela ya go tswa ya A ba ne ba dirisa tsela ya go tswa ya B, palo ya ba ba dirisitseng tsela ya go tswa ya C ke 700-420 = 280 baithuti.
#### 280 

Joan is 20 + 5 = <<20+5=25>>25 years old.
Mary is 25 – 2 = <<25-2=23>>23 years old.
Therefore, the sum of their ages is 20 + 25 + 23 = <<20+25+23=68>>68.
#### 68