функции кнопок

app/src/main/res/layout/activity_proekt2.xml

@@ -11,6 +11,7 @@
     android:text="Курс доллара"
     android:textSize="40dp"
     app:layout_constraintEnd_toEndOf="parent"
-    app:layout_constraintBottom_toTopOf="parent"
-    app:layout_constraintStart_toStartOf="parent"/>
+    app:layout_constraintStart_toStartOf="parent"
+    app:layout_constraintTop_toTopOf="parent"
+    />
 </androidx.constraintlayout.widget.ConstraintLayout>