at that point I start recycling them, and go back to parenthesis.

so when bp = 300x - 3, this:

4( 4[ 4{ 15bp + 10 } - 375 ] - 2250 ) - 15000

would turn to

4( 4[ 4{ 15( 300x - 3) + 10 } - 375 ] - 2250 ) - 15000

perhaps not the best, but I rather stick to conventional symbols rather than using... idk, question marks? that'd be funny as hell, though

just picture it:

4© 4« 4¿ 15bp + 10 ? - 375 » - 2250 🄯 - 15000