Answer:
José has 49 used stamps
Step-by-step explanation:
7 used stamps for every 4 new stamps
To solve this type of problem, we can use a ratio
7 : 4 ratio
He has 28 new stamps
7 : 4 = x : 28
Ratios can be written as fractions
Cross multiply
4x = 7(28) = 196
Divide by 4 on both sides
x = 49
Hope this helps :)