diff --git a/sose2021/algebra/alg3.pdf b/sose2021/algebra/alg3.pdf
new file mode 100644
index 0000000..267caee
Binary files /dev/null and b/sose2021/algebra/alg3.pdf differ
diff --git a/sose2021/algebra/alg3.xopp b/sose2021/algebra/alg3.xopp
new file mode 100644
index 0000000..0425c7d
Binary files /dev/null and b/sose2021/algebra/alg3.xopp differ