Let index 1 refer to the pisyon with smaller section. And index 2, to the other piston.
F1=20N
S1=0.2m²
S2=2m².
a) pressure p= F1/S1=F2/S2.
We get: p=F1/S1=20N/0.2m²=100N/m²
b) force on the other piston:
F2=p×S2
F2=100N/m²×2m²=200N
Answer: p=100N/m², F2=200N