First, to make everything easier,divide each side by 2 :
x = 2a + 2b
There's the solution for ' x '.
Now, if you want it solved for ' a ' , then subtract ' 2b ' from each side :
x - 2b = 2a
and divide each side by 2 : a = 1/2 (x - 2b)
and if you want it solved for ' b ' then subtract ' 2a ' from each side :
x - 2a = 2b
and divide each side by 2 : b = 1/2 (x - 2a) .