-10369
too lazy but that's the exact value
First, factor out 5:
5 (x² -x -20)
We need two numbers that add to -1 and multiply to -20. -5 and 4 satisfy this.
5(x-5)(x+4)
Subtract what has already been loaded from total amount allowed:
23500 - 9700 = 13,800
Divide the amount left by the weight of each crate:
13,800 / 70 = 197.14
They can load 197 crates.