Explanation:

It’s given that: 3²⁰¹⁹ is divided by 10.
Now, 3¹ = 3
3² = 9
3³ = 27
3⁴ = 81
3⁵ = 243
3⁶ = 729
Since, unit place of the power of 3 repeats after every 4 steps (i.e. it has a cyclicity of 4).
Now, on dividing 2019 by 4 we get a remainder of 3.
Hence, 3²⁰¹⁹ will have the same last digit as that of 3³, i.e. 7.
(3³)/10 = 27/10
Hence, the remainder will be 7.