The digit at unit place of the number $$3^{99} - 3^{50}$$​ is-

We need to find the unit digit of the expression:
​$$3^{99} − 3^{50}$$​​

Concept used:
The unit digit of powers of 3 follows a 4-digit repeating cycle:
$$3^1$$​ = 3 → unit digit 3
$$3^2$$​ = 9 → unit digit 9
$$3^3$$​= 27 → unit digit 7
$$3^4$$​ = 81 → unit digit 1
Then it repeats: 3, 9, 7, 1...

So, to find the unit digit of 3 raised to any power, divide the exponent by 4 and check the remainder.

99 ÷ 4 gives remainder 3 → So, unit digit of $$3^{99}$$​ = 7

50 ÷ 4 gives remainder 2 → So, unit digit of  $$3^{50}$$​ = 9

Now subtract the unit digits:
7 − 9 = -2

Since unit digits can't be negative, add 10:
-2 + 10 = 8