If we let x be the measure of the side of the squares that are to be cut out of the cardboard to form the box. The new dimensions of the base will then be:
Length = 12 - 2x
Width = 10 - 2x
The area is calculated by multiplying the length and width.
Area = L x W
Substituting the expressions,
80 = (12 - 2x)(10 - 2x)
The value of x from the equation is 1.
The size of the square should be 1 in x 1 in.