The sum of 7+7+7+7 could be represented by the multiplication expression of 7x4.
This is because in multiplication, the x4 referst to the times that the same first number (7) is going to be added. So, in the case of 7x4, the number 7 is going to be added 4 times. That is, 7+7+7+7.
As we can see, both expressions arrive to the same result, which is 28.