Answer:
See explanation.
Step-by-step explanation:
The 'base' of a rectangular prism refers to only one side of the rectangular prism, which is a rectangle.
The formula for the area of a rectangle is as follows:

Where A = area, l = length, and w = width.
The 'base' of a cylinder refers to only one side of the cylinder, which is a circle.
The formula for the area of a circle is as follows:

Where A = area and r = radius.
Just in case you typed your question incorrectly and were asking for surface area, here is the formula for surface area for both as well:
Rectangular prism: 
Cylinder: 
Answer:

Step-by-step explanation:

Add 4 to both sides

Divide both sides by 3

Hope this helps!
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Answer:
12
Step-by-step explanation:
These triangles are similar using the AA theroem. This means there sides are in corresponding proportion.
Side AR and Side TE are corresponding. Use this proportion.

This side the triangle SAR side lengths are 3/4 of side lengths of triangle SET.
We know that RS+ST=21
And that RS=3/4(ST).


x=12.
Side ST is 12