$3.95
x will represent the cost of one box of cereal.
98.75 = 25x
We want to get x by itself on one side of the equation, so to cancel out the multiplication by 25, we need to divide by 25. Also, what we do on one side of the equation, we must do to the other side. So, divide both sides of the equation by 25.
3.95 = x
So, one box of cereal costs $3.95.
