+129 John has US and foreign stamps in his album. The ratio of the number of US stamps to foreign stamps is 5 : 2. After Paul gives him 12 foreign stamps, the ratio becomes 2 : 1. Find the number of US stamps he has.
+208 d=number of domestic stamps
f=number of foreign stamps
\(\:\frac{d}{f}=\frac{5}{2}\)
\(2d=5f\)
\(\frac{d}{f+12}=\frac{2}{1}\)
\(d=2f+24\)
substitute d in first equation:
\(2(2f+24)=5f\)
\(f=48\)
\(d=120\)
JP
+208 d=number of domestic stamps
f=number of foreign stamps
\(\:\frac{d}{f}=\frac{5}{2}\)
\(2d=5f\)
\(\frac{d}{f+12}=\frac{2}{1}\)
\(d=2f+24\)
substitute d in first equation:
\(2(2f+24)=5f\)
\(f=48\)
\(d=120\)
JP
