tom and adam have a total of 240 stamps. The ratio of the number of tom's stamps to adam's is 3:7. Tom buys some stamps from Adam. The ratio of tom's stamp to adam's is now 3:5. How many stamps does tom buy from adam

18

Step-by-step explanation:

In both cases, the number remains constant, 240 stamps.

Given that 3:7 is equal to 3/10 to 7/10

Initially, Tom had 3/10*240=72 stamps

Finally, 3:5 equal to 3/8 to 5/8

Tom has 3/8*240=90 stamps

Difference is 90-72=18 stamps

Therefore, Tom bought 18 stamps from Adam and Adam didn't replace