Description for Correct answer:
Let the number of gold coins initially be x

and the number of non-gold coins be y.

According to the question,

3x = y

When 10 more gold coins, total number gold coins become x + 10

and the number non-gold coins remain the same at y.

Now, we have \( \Large 2 \left(10+x\right)=y \)

Solving these two equations, we get

x = 20 and y = 60.

Total number of coins in the collection at the end is equal to

x+10+y = 20+10+60 = 90.