Awindow is 21 inches wide, and its perimeter is 112 inches. what is the length of the window?

The length of the window is 35 inches.  

Step-by-step explanation:

Perimeter of an object can be found using the general formula:  P = 2W + 2L, where P = perimeter, W = width and L= length.  Since both the width and perimeter of the window are given, we can plug these values into the formula to solve for the missing variable 'L':  112 = 2(21) + 2L, or 112 = 42 + 2L.  We can then use inverse (opposite) operations to isolate the variable and solve.  Whatever we do to one side of the equation, we do to the other.  We will start by subtracting 42 from each side:  112 - 42 = 42 - 42 + 2L or 70 = 2L.  Next, we divide both sides by 2 to solve for L:  70/2 = 2L/2 or L = 35.  So, the final length of the window is 35 inches.  

see explanation

step-by-step explanation:

a

(6r + 7) + (13 + 7r) ( remove brackets and collect like terms )

= 6r + 7 + 13 + 7r

= 13r + 20

b

remove brackets and collect like terms

13 - r - 1 + r

= 12 - r

c

remove brackets and collect like terms

= - 8 - r + 2r - 4

= - 12 + r

d

remove brackets and collect like terms

= 7r - - - 6r

[-   - = - - = - ]

= r -

inverse property is the answer

step-by-step explanation: