I thought no. 9 was similar in difficulty to no. 7
This one didn’t just have an arithmetic mistake, I also copied the wrong number from the equation. I didn’t recalculate that since I knew the structure of the tree was correct. I think that mistake matters. I think fixing the mistake just requires more focus and practicing more trees?
I thought to include the expression I used in wolphramalpha for the last tree. It was:
(6(3-4)(4-6^2))/(2+4)-(5+2)/(6(1-3))