Question 205621
 Dave and Jane Wells have a new rectangular driveway. The perimeter of the driveway is 168 feet. The length is 12 feet longer than three times the width. What are the dimensions of the driveway?
Let the width be represented  by w and the length by l.
You are told the perimeter is 168 feet. And you know the perimeter of a rectangle is given by {{{P = 2l + 2w}}}
You are told {{{l = 3w + 12}}}

Now using those two equations, solve for w as follows:
{{{P = 2l + 2w}}}
{{{168 = 2*(3w + 12) + 2w}}}
{{{168 = 6w + 24 + 2w}}}
{{{168 - 24 = 8w}}}
{{{144 = 8w}}}
{{{18 = w}}}
Now find l
{{{l = 3*18 + 12}}}
{{{l = 54 + 12}}}
{{{l = 66}}}
Check your answer. Does {{{168 = 2*66 + 2*18}}} ???


 A leather coin purse has the shape of a triangle. Two sides are equal in length and the third side is 3 centimeters shorter than one and one-half times the length of the equal sides. The perimeter is 28.5 centimeters. Find the lengths of the sides.
Use the same process on this one. However, this time the shape is a triangle.
So the perimeter is given as {{{P = a + b + c}}} where a,b and c are the length of the three sides.

You are told the perimeter is 28.5 and that two sides are equal in length. Let the length of one of the equal sides be given by a. Since the second side, b, is equal, then b = a.
You are also told the third side, c, is given by {{{c = 1.5a - 3}}}

Now you have everything you need to solve
{{{P = a + b + c}}}
{{{28.5 = a + a + (1.5a -3)}}}
{{{28.5 = 3.5a - 3}}}
{{{31.5 = 3.5a}}}
{{{9 = a}}}
Since b = a, b is also 9
{{{c = 1.5a - 3}}}
{{{c = 1.5 * 9  - 3}}}
{{{c = 13.5 - 3}}}
{{{c = 10.5}}}
Check your answer, does {{{28.5 = 9 + 9 + 10.5}}}

This same set of steps works for all these perimeter type problems.