Area = 3150 ft²
Unknown Side = 45 ft²
First, you know two of the sides of the shape have a length of 70 ft. So you subtract 140 (which is 70 · 2) from 230 and get 90. 90 is the total length of the two unknown sides. In order to find one side you divided 90 by 2. Here is the work I did:
70 · 2 = 140
230 - 140 = 90
90 ÷ 2 = 45
45 is the length of the unknown side.
Now to find area:
Area = length × width
Area = 45 x 70
Area = 3150 ft²
Note that saying "ft squared" is very important because it lets the reader know that it is a 2D shape.
