Ratio and Proportions
posted by Dottie on .
Salina had some local and foreign stamps. The ratio of the number of local stamps to the number of foreign stamps was 3:4. She bought 21 more local stamps and the ratio became 9:8.
a. How many foreign stamps did Salina have?
b. How many local stamps did Salina have in the end?

using d for domestic and f for foreign,
d/f = 3/4
(d+21)/f = 9/8
42 local stamps
56 foreign stamps
check: 42/56 = 3/4
63/56 = 9/8