Aidan has four cards with +, -, x, ÷ printed on them.
He inserts them between the five numbers 5, 4, 3, 2 and 1 to form the expression 5 + 4 x 3 -2 , which the value 15.
Emma says:
"Aidan put the operation in the order +, -, x, ÷.
If I place the operation cards in a different order between the number 5, 4, 3, 2, 1. I can make the value equal to 19."
Which operation would Emma do first?