please also show steps on how to solve for a 2239 x 104 2 a

please also show steps on how to solve for a.

(2.239 x 10^-4) ^2 / (a - 2.239 x 10^-4) = 8.90 x 10^-7

the answer is a= .0565 but im not sure how that was determined

Solution

It is just cross multiplication problem.
Given
(2.239 x 10^-4) ^2 / (a - 2.239 x 10^-4) = 8.90 x 10^-7
do cross multiplication,
(2.239 x 10^-4) ^2 / (8.90 x 10^-7)= a - 2.239 x 10^-4
a - 2.239 x 10^-4 = 0.05633
a = 0.05655