Rearrange the formula = a/b=c/d+e/f e to make f the subject?

Answer:

20) C

a = c + e
b d f

Let us first solve the right hand side (RHS).

c + e
d f

cf + ed
df

a = cf + ed
b df

adf = b (cf + ed)

adf = bcf + bed

adf – bcf = bed
f (ad – bc) = bed

f = bde
ad – bc