Google sheets Specialization Efficiency Formula

This formula will pull a number you input (05) and tell you the percentage discount you get in your crafting recipes.
=IF(B13=0,0,(((B131)*15)+20)*0.01)
This cell is D13. So to find out how many logs I need with efficiency 5 if the original is 10 I do this:
=(1010*$D$13)
so, we take the original quantity, 10 and multiply it by the D13 cell. Make sure to include the $ signs, because this tells google sheets to always use that specific square even if you paste this formula somehwere else. Just update that number to whatever efficiency skill is represented. 10 * D13 will get us the percentage of items we are saving, so we subtract that from our original amount of 10.
Maybe not the best formula, and please let me know if I can improve, but it should help some people out to make dynamic spreadsheets.