Answer:
After one month, Xian and his cousin will have 84 stamps each.
Step-by-step explanation:
Let x represent number of months.
We have been given that Xian's club will send him 20 new stamps per month. Number of stamps that Xian would have after x months would be [tex]20x[/tex].
Total number of stamps that Xian would have after x months would be [tex]20x+64[/tex].
We are also told that Kai's club will send him 16 new stamps per month. Number of stamps that Kai would have after x months would be [tex]16x[/tex].
Total number of stamps that Kai would have after x months would be [tex]16x+68[/tex].
Now, we will equate both expressions and solve for x.
[tex]20x+64=16x+68[/tex]
[tex]20x-16x+64=16x-16x+68[/tex]
[tex]4x+64=68[/tex]
[tex]4x+64-64=68-64[/tex]
[tex]4x=4[/tex]
[tex]\frac{4x}{4}=\frac{4}{4}[/tex]
[tex]x=1[/tex]
Therefore, after 1 month Xian and Kai will have same stamps.
[tex]16x+68[/tex]
[tex]16(1)+68[/tex]
[tex]16+68=84[/tex]
[tex]20x+64[/tex]
[tex]20(1)+64[/tex]
[tex]20+64=84[/tex]
Therefore, after one month, Xian and his cousin will have 84 stamps each.