Alex and Freddy collect stamps. The number of stamps in Alex's collection is in ratio 3:5 to the number of stamps in Freddy's collection. If Freddy gives Alex 10 stamps, the ratio will change to 7:9. How many stamps are in both collections together?

Suppose Alex has 3x stamps, Freddy has 5x stamps. After Freddy gives Alex 10 stamps, Alex has 3x+10 while Freddy has 5x-10

the new ratio is 7 to 9, so we have the equation: (3x+10) / (5x-10) = 7/9

9 (3x+10) = 7 (5x-10)

27x+90=35x-70

160=8x

x=20

So Alex has 3*20=60 stamps while Freddy has 5*20=100. Together they have 160