Answer:
x = 120 trees
Explanation:
Since the trees he has left produces 130 apples each, and he ended up with 11 700 apples, it means he has left 11 700 / 130 = 90 trees.
Now, since he lost 30 trees in the fire, it means before he had 30 more trees => 90 + 30 = 120 trees
The equation for it:
( x - 30 ) * 130 = 11 700
x - 30 = 11 700 / 130
x = 90 + 30
x = 120