Index: src/activities/memory-math-minus/resource/1/Data.qml
===================================================================
--- src/activities/memory-math-minus/resource/1/Data.qml
+++ src/activities/memory-math-minus/resource/1/Data.qml
@@ -24,7 +24,7 @@
 
 Data {
     objective: qsTr("Subtraction table of 1.")
-    difficulty: 1
+    difficulty: 4
 
     data: [
         { // Level 1
Index: src/activities/memory-math-minus/resource/2/Data.qml
===================================================================
--- src/activities/memory-math-minus/resource/2/Data.qml
+++ src/activities/memory-math-minus/resource/2/Data.qml
@@ -24,7 +24,7 @@
 
 Data {
     objective: qsTr("Subtraction table of 2.")
-    difficulty: 1
+    difficulty: 4
 
     data: [
         { // Level 1
Index: src/activities/memory-math-minus/resource/3/Data.qml
===================================================================
--- src/activities/memory-math-minus/resource/3/Data.qml
+++ src/activities/memory-math-minus/resource/3/Data.qml
@@ -24,7 +24,7 @@
 
 Data {
     objective: qsTr("Subtraction table of 3.")
-    difficulty: 2
+    difficulty: 4
 
     data: [
         { // Level 1
Index: src/activities/memory-math-minus/resource/4/Data.qml
===================================================================
--- src/activities/memory-math-minus/resource/4/Data.qml
+++ src/activities/memory-math-minus/resource/4/Data.qml
@@ -24,7 +24,7 @@
 
 Data {
     objective: qsTr("Subtraction table of 4.")
-    difficulty: 2
+    difficulty: 4
 
     data: [
         { // Level 1
Index: src/activities/memory-math-minus/resource/5/Data.qml
===================================================================
--- src/activities/memory-math-minus/resource/5/Data.qml
+++ src/activities/memory-math-minus/resource/5/Data.qml
@@ -24,7 +24,7 @@
 
 Data {
     objective: qsTr("Subtraction table of 5.")
-    difficulty: 3
+    difficulty: 4
 
     data: [
         { // Level 1
Index: src/activities/memory-math-minus/resource/6/Data.qml
===================================================================
--- src/activities/memory-math-minus/resource/6/Data.qml
+++ src/activities/memory-math-minus/resource/6/Data.qml
@@ -24,7 +24,7 @@
 
 Data {
     objective: qsTr("Subtraction table of 6.")
-    difficulty: 3
+    difficulty: 5
 
     data: [
         { // Level 1
Index: src/activities/memory-math-minus/resource/7/Data.qml
===================================================================
--- src/activities/memory-math-minus/resource/7/Data.qml
+++ src/activities/memory-math-minus/resource/7/Data.qml
@@ -24,7 +24,7 @@
 
 Data {
     objective: qsTr("Subtraction table of 7.")
-    difficulty: 4
+    difficulty: 5
 
     data: [
         { // Level 1
Index: src/activities/memory-math-minus/resource/8/Data.qml
===================================================================
--- src/activities/memory-math-minus/resource/8/Data.qml
+++ src/activities/memory-math-minus/resource/8/Data.qml
@@ -24,7 +24,7 @@
 
 Data {
     objective: qsTr("Subtraction table of 8.")
-    difficulty: 4
+    difficulty: 5
 
     data: [
         { // Level 1