Question 541752
"A 120-page book has p lines to a page.
 If the number of lines were reduced by three on each page, the number of pages would need to be increased by 20 to give the same amount of writing space.
 How many lines were there on the page originally?
:
Let p = no.  of pages originally
:
120p = no. of lines originally
then
140(p-3) =  when page lines are reduced by 3, and pages increased by 20
:
Total no. of lines remain the same, therefore the equation is:
140(p-3) = 120p
140p - 420 = 120p
140p - 120p = 420
20p = 420
p = {{{420/20}}}
p = 21 lines per page originally
:
:
Prove this by seeing the total number of lines remain the same.
120*21 = 2520 lines
140*18 = 2520