To find the area of the square base, you will use the information given about the area of the lateral side to find the missing base length.
First, divide the total lateral area by 4 because there are 4 congruent lateral faces.
107.25/4 = 26.8125
Use this in the formula for area of a triangle.
A = 1/2 x b x h
26.8125 = 1/2 x b x 8.25
26.8125 = 4.125b
b = 6.5 cm
The length of the base edge is 6.5 centimeters.