Answer:
length=138ft
width=32ft
138:32
69:16
ratio=69/85:16/85
Step-by-step explanation:

Given:
The sum of the first three terms of a sequence Is 42.
The fourth term is 24.
To find:
The u₁ and the common difference
Step-by-step explanation:
nth term of a sequence is

where, u₁ is first term and d is common difference.
4th term is 24.

...(i)
Sum of nth term of an AP is
![S_n=\dfrac{n}{2}[2u_1+(n-1)d]](https://tex.z-dn.net/?f=S_n%3D%5Cdfrac%7Bn%7D%7B2%7D%5B2u_1%2B%28n-1%29d%5D)
Sum of first three terms is 42.
![S_3=\dfrac{3}{2}[2u_1+(3-1)d]](https://tex.z-dn.net/?f=S_3%3D%5Cdfrac%7B3%7D%7B2%7D%5B2u_1%2B%283-1%29d%5D)
![42=\dfrac{3}{2}[2u_1+2d]](https://tex.z-dn.net/?f=42%3D%5Cdfrac%7B3%7D%7B2%7D%5B2u_1%2B2d%5D)
Divide both sides by 3.
...(ii)
On subtract (ii) from (i), we get


Put d=5 in equation (ii).
Therefore, the first term is
and common difference is
.
The answer is 18.
I hope this helps :D