bill rate / pay rate calcs

I have attached a spreadsheet ... there are 3 sets of data in it

the first one works perfectly and has a formula for calculating the gross profit % given 4 variables: burden, 3rd party adjustment, bill rate and pay rate. I am looking for 2 formulas: 1 that calculates the bill rate given the other 4 variable are known and 1 that calculates the pay rate given the other 4 variables.

I can't seem to get it right.

thank you for your help.