​​​If  $$3^{3x+2y} = 81$$​ and $$5^{x-2y}$$​ = 625,  then 5x + 3y  is:

Correct option is A

Given:​

$$3^{3x+2y} = 81$$​​ and $$5^{x-2y} = 625$$​

Solution: ​

​$$3^{3x+2y} = 81\\ \ \\ 3^{3x+2y} = 3^4$$​
comparing power 

3x+2y = 4....(1) 

Now, 

​$$5^{x-2y} = 625 \\ \ \\ 5^{x-2y} = 5^4$$ 

comparing power

x - 2y = 4 ....(2) 

adding eq(1) and (2) 

4x = 8 

x = 2 

then, y = -1 

Now, 5x + 3y = 5(2) +3(-1) = 10 - 3 = 7