Question 783659
Let L be the length and W be the width


It says that "the width is 7cm less than the length", so we know that W = L - 7


The formula for the perimeter of a rectangle is 


P = 2L + 2W


P = 2L + 2(L - 7) ... plug in W = L - 7 (replace W with L - 7)


34 = 2L + 2(L - 7) ... plug in P = 34 (the given perimeter)



Now we solve for L


34 = 2L + 2(L - 7)


34 = 2L + 2L - 14


34 = 4L - 14


34+14 = 4L


48 = 4L


4L = 48


L = 48/4


L = 12


<font color="red">The length is <b>12 cm</b>.</font>


Now turn to W = L - 7 and plug in L = 12


W = L - 7


W = 12 - 7


W = 5


<font color="red">And the width is <b>5 cm</b>.</font>