Respuesta :
Answer:
Harry collected 180 stamps
Harry's sister collected 60 stamps
Step-by-step explanation:
Let X be the number of stamps that Harry's sister colleted.
The number of stamps Harry colleted is 3 time as many as his sister's
⇒ 3*X + X = 240
⇒ X = 60
⇒ 240 - 60= 180
