Alan and Bala has some erasers. 1/5 of the number of erasers Alan has was equal to 2/3 or the number of erasers Bala has. Alan has 21 erasers more than Bala. How many erasers does Bala Rave?

Let's say Alan has x erasers.

Therefore, 1/5*x = 2/3*x - 21
Multiply by 15 both sides of the equation:
3*x = 10*x - 315
Simplifying the right side, we get:
10*x - 3*x = 315
7*x = 315
So x, the number of erasers Alan has, is equal to 315/7 = <<315/7=45>>45 erasers.
This also means that Bala has 45 - 21 = <<45-21=24>>24 erasers. Answer: \boxed{24}.

Let's assume the number of erasers Alan has as "A" and the number of erasers Bala has as "B".

According to the given information, we can create two equations:

1) (1/5)A = (2/3)B -- (equation 1)
2) A = B + 21 -- (equation 2)

To solve this system of equations, we can first simplify equation 1 by multiplying both sides by 15:

15 * (1/5)A = 15 * (2/3)B

3A = 10B

We can rewrite equation 2 as:

A - B = 21

Now we have a system of equations:

3A = 10B -- (equation 3)
A - B = 21 -- (equation 4)

To eliminate one variable, we can multiply both sides of equation 4 by 10:

10A - 10B = 210

Now we can substitute the value of 10B from equation 3 into this equation:

10A - 3A = 210

7A = 210

Dividing both sides by 7, we find:

A = 30

Substituting the value of A back into equation 4, we can solve for B:

30 - B = 21

B = 30 - 21

B = 9

So, Bala has 9 erasers.