diff --git a/EasyLean.lean b/EasyLean.lean
index a53489d..ada949a 100644
--- a/EasyLean.lean
+++ b/EasyLean.lean
@@ -1 +1 @@
-import EasyLean.Basic
+import EasyLean.Mathd.Algebra.mathd_algebra_513
diff --git a/EasyLean/Basic.lean b/EasyLean/Basic.lean
index 305e1ca..ada949a 100644
--- a/EasyLean/Basic.lean
+++ b/EasyLean/Basic.lean
@@ -1,12 +1 @@
-import Mathlib.Data.Real.Basic
-import Mathlib.Tactic.Linarith
-
-theorem mathd_algebra_513
-  (a b : ℝ)
-  (h₀ : 3 * a + 2 * b = 5)
-  (h₁ : a + b = 2) :
-  a = 1 ∧ b = 1 := by
-  sorry
-
-theorem eq_four : ∀ a b c d : Nat, a = b → a = d → a = c → c = b := by
-  sorry
+import EasyLean.Mathd.Algebra.mathd_algebra_513
diff --git a/EasyLean/Mathd/Algebra/mathd_algebra_513.lean b/EasyLean/Mathd/Algebra/mathd_algebra_513.lean
new file mode 100644
index 0000000..ea83c72
--- /dev/null
+++ b/EasyLean/Mathd/Algebra/mathd_algebra_513.lean
@@ -0,0 +1,9 @@
+import Mathlib.Data.Real.Basic
+import Mathlib.Tactic.Linarith
+
+theorem mathd_algebra_513
+    (a b : ℝ) (h₀ : 3 * a + 2 * b = 5) (h₁ : a + b = 2) :
+    a = 1 ∧ b = 1 := by
+  constructor
+  · linarith [h₀, h₁]
+  · linarith [h₀, h₁]