1 files changed, 7 insertions, 1 deletions
diff --git a/src/act4e_solutions/sets_properties.py b/src/act4e_solutions/sets_properties.py
index 5390d23..2044abd 100644
--- a/src/act4e_solutions/sets_properties.py
+++ b/src/act4e_solutions/sets_properties.py
@@ -7,7 +7,13 @@ X = TypeVar("X")
 
 class SolFiniteSetProperties(I.FiniteSetProperties):
     def is_subset(self, a: I.FiniteSet[X], b: I.FiniteSet[X]) -> bool:
-        raise NotImplementedError()
+        return all([b.contains(e) for e in a.elements()])
+
+    def equal(self, a: I.FiniteSet[X], b: I.FiniteSet[X]) -> bool:
+        return self.is_Subset(a, b) and self.is_subset(b, a)
+
+    def is_strict_subset(self, a: I.FiniteSet[X], b: I.FiniteSet[X]) -> bool:
+        return self.is_subset(a, b) and not self.is_subset(b, a)
 
 
 class SolFiniteMakeSetUnion(I.FiniteMakeSetUnion):