A square animal pen and a pen shaped like an equilateral triangle have equal perimeters. Find the length of the sides of each pen if the sides of the triangular pen are 15 less than twice a side of the square pen. (Hint: An equilateral triangle has three sides the same length.)

You have 30 yards of fencing with which to make a rectangular pen. Let x be the length of the pen. You want the pen to have greatest possible area. What length and width should you use? Explain your reasoning.

Fencing comes in 3-m pieces. How many pieces should you buy to enclose a square with 7-m sides?

A square has sides of length 2k - 1 units. An equilateral triangle has sides of length k + 2 units. The square and the triangle have the same perimeter. What is the value of k?

A square animal pen and a pen shaped like an equilateral triangle have equal perimeters. Find the length of the sides of each pen if the sides of the triangular pen are fifteen less than twice the sides of the square pen.

The height h (in feet) of a javelin thrown at a track and field competition can be modeled by $h=-16 t^{2}+50 t+6,$ where t is time in seconds. After how many seconds is the javelin 30 feet above the ground?