when two resistors of resistances R(1) and R(2) (the numbers are the subscripts) are connected in parallel, their combined resistance is

R(1) R(2) / R(1) + R(2). two resistors are found to have a combined resistance of 10 ohms (thats just a variable, im assuming) when connected in series, and 2 ohms when connected in parallel. what is the resistance of each? it would be best to use X as the variable. thanks!