Let, she sold x and y numbers of succulent and ivy plants.
So,
x + y = 34 ...1)
12x + 4y = 240 ...2)
Putting value of x from 1) to 2), we get :
12( 34 -y ) + 4y = 240
408 - 12y + 4y = 240
8y = 168
y = 21
x = 13
Therefore, she sell 13 succulent and 21 ivy plants.
Hence, this is the required solution.