Really need help transposing this simple question.

so ((a+b)cd) / e = f?


( (a+b)(c)(d) ) / e = f
multiply by e:
( (a+b)cde ) / e = ef
(a+b)cd = ef
divide by (a+b)c:
( (a+b)cd)) / (a+b)c  = ef/((a+b)c)
d = ef / ((a+b)c)


the brackets and fraction make it a little more intimidating, but you're still using the same algebra to move variables around. with practice it will become easier to see what steps you need to take to isolate the variable you want!