Question 78874
Set up a ratio of {{{length/width}}}
{{{1.5/1=21/x}}}
Notice the length is the numerator of both fractions, and width is in the denominator. Now, Just solve for x and you will have your width:
{{{1.5=21/x}}}
{{{1.5x=21}}}
{{{x=21/1.5}}}cm
I will let you work out the last step.
Good Luck,
tutor_paul@yahoo.com