Andres company manufactures rectangular storage sheds decisions are made with aluminum side panels that measure 8 feet 10 feet 12 feet and 15 feet along the bottom edge for example one possible shed measures 12 feet by 15 feet list the measurements of all the possible sets

The formula for combinations is
C=n!/[(n-r)!*r!]
where
n is the total number of objects you choose from
r is the number that you choose to arrange

in this problem
n=4 aluminum side panels measures

r=2 aluminum side panels measures

C=4!/[(4-2)!*2!]> C=4!/[2!*2!]---> (4*3*2!)/(2!*2*1)
C=6

1) 8 ft x 10 ft

2) 8 ft x 12 ft

3)8 ft x 15 ft

4) 10 ft x 12 ft

5) 10ft x 15 ft

6) 12 ft x 15 ft

additionally, we have each measure with itself

7) 8 ft x 8 ft

8) 10 ft x 10 ft

9) 12 ft x 12 ft

10) 15 ftx 15 ft

the answer is

10 possible sets