Question 1108972
R, words per month
T, number of months of time
W, number of words
{{{W/T=R}}}
R is a separate constant depending on which country.

<pre>
COUNTRY        RATE        TIME       WORDS
A              130          t         130t
B              150         14-t      150(14-t)
Totals                      14        1920
</pre>

{{{highlight_green(130t+150(14-t)=1920)}}}

-

{{{13t+15(14-t)=192}}}
{{{13t+15*14-15t=192}}}
{{{-2t=192-15*14}}}
{{{2t=18}}}
{{{highlight(t=9)}}}--------9 months in country A
-
{{{highlight(5)}}}---------5 months in country B