Question 183453
Call the certain number of pages 1 job
Call the 1st machine's rate of printing pages {{{r}}}
Then the 2nd machines rate is {{{r/2}}}
Working together, their combined rate is {{{1/8}}}
which is 1 job in 8 minutes
I can add the 2 rates to get the combined rate
{{{r + r/2 = 1/8}}}
{{{8r + 4r = 1}}}
{{{12r = 1}}}
{{{r = 1/12}}}
This means the 1st machine, working alone, 
can print the pages in 12 minutes
{{{r/2 = (1/12)/2}}}
{{{r/2 = 1/24}}}
This means the 2nd machine, working alone, 
can print the pages in 24 minutes
check answer:
{{{r + r/2 = 1/8}}}
{{{1/12 + 1/24 = 1/8}}}
Multiply both sides by {{{24}}}
{{{2 + 1 = 3}}}
{{{3 = 3}}}
OK