How do you solve the equation 1over s equals 1 over b plus 1 over c?

Answer 1

What do you want it solved for ?

's' ? or 'b' ? or 'c' ?

Since this is the formula for the total effective resistance of two parallel resistors,
the inductance of two parallel coils, and the capacitance of two series capacitors,
as well as the "lensmaker's formula" that relates the image distance, object distance,
and focal length of a lens, it's probably the most useful to solve it for 's', and I will now
do so. I shall require total silence from members of the audience.

1/s = 1/b + 1/c

Multiply each side by 'bc':

bc/s = bc/b + bc/c
bc/s = c + b

Multiply each side by 's':

bc = s (c + b)

Divide each side by (c + b):

bc/(c+b) = s

This is the handy form that's easy to remember ... it's "the product over the sum".