The answer is: 5,614 square inches.
The explanation is shown below:
1. The gift on the bottom is a rectangular prism. To calculate its surface area, you must apply the following formula:
[tex]SA=2[(l)(w)+(l)(h)+(h)(w)][/tex]
Where [tex]l[/tex] is the length (20 inches), [tex]w[/tex] is the width (42 inches) and [tex]h[/tex] is the heigth (16 inches).
2. Substitute values:
[tex]SA1=2[(20in)(42in)+(20in)(16in)+(16in)(42in)]=3,664in^{2[/tex]
3. The surface area of the other gifts can be calculated with the formula for calculate the surface area of a cube:
[tex]SA=6s^{2}[/tex]
Where [tex]s[/tex] is the side.
4. The surface area of the bigger cube is:
[tex]SA2=6(15in^{2})=1,350in^{2}[/tex]
5. The surface area of the smaller cube is:
[tex]SA3=6(10in^{2})=600in^{2}[/tex]
6. The total surface area (the combined surface area of the three gifts) is:
[tex]SAt=SA1+SA2+SA3\\SAt=3,664in^{2}+1,350in^{2}+600in^{2}\\SAt=5,614in^{2}[/tex]
