Question 659734
pen = pencil+12 and 10pencil +8pen = 339.<P>
Two equations and two unknowns.  Use the first equation to substitute the value of pen in terms of pencils into the second equation and solve it.<P>
10pencil + 8(pencil+12) = 339<P>
10pencil +8pencil + 96 = 339<P>
18pencil = 243<P>
pencil = 13.5<P>
pen = pencil + 12 = 13.5+12 = 25.5