Question 747270
we need to solve

x=y(b/(a+b)) for b

divide both sides of = by y

x/y = b/(a+b)

cross multiply the two fractions and we get

x(a+b) = yb

xa+xb = yb

now group the terms with b on to same side of = sign

yb-xb = xa

factor out the b

b(y-x) = xa and

b = xa/(y-x)