If you would like to know how many muffins did Elsa bake, you can calculate this using the following steps:
2/5 of all of the muffins = 4 muffins
2/5 * x muffins = 4
2/5 * x = 4 /*(5/2)
x = 4 * 5/2
x = 10 muffins
The correct result would be 10 muffins.