Answer :
Answer:
See below in bold.
Step-by-step explanation:
Let Anna's, Boris and Clara's numbers be a b and c.
a + 20 = b - 22 + 21
b - 20 = c + 22 + 21
a + 20 = b - 1
b - 20 = c + 43
a - b + 20 = -1
Adding the last 2 equations:
a = c + 42
c = a - 42
So Clara's number is 42 less then Anna's number.