Miko and Cheko each had an equal number of stamps. On Cheko's birthday, Miko gave Cheko 31 stamps. After receiving the stamps from Miko, Cheko had 3 times as many stamps as Miko. How many stamps had Cheko in the end?

Let n = initial number of stamps

We are told: n + 31 = 3*(n - 31)

I'll leave you to determine n from this and hence the number, (n + 31), that Cheko ended up with.