p=1/r.s+d for s please help me!!!???

if you mean

p = 1/(rs) + d then
p-d = 1/(rs)
rs = 1/(p-d)
r = s/(p-d)

Or, if you mean

p = 1/(rs+d) then
rs+d = 1/p
rs = 1/p - d = (d-p)/p
r = (d-p)/(sp)

Thank you!!

it says solve for s, not r