Answer:
11.
Step-by-step explanation:
N = Nadia.
P = Pete.
S = postcards that Nadia gives to Pete.
N = 20 + P
P + S = 2+N-S
To calculate S, we replaces N of the first equation in the second equation:
P + S = 2 + 20 + P-S
2S = 2 + 20 + P - P
2S = 22
S = 22/2 = 11.
