Algebra Question! Please Help!

Question

Find a: (st)/(r) + (x)/(a+b) = (z/y)

(A) (-bsty - rxy + brz)/(sty - rz)

(B) x ((-(r)/(st) - (b/x) + (y/z))

(C) ((ry)(st + x - z))/(-b)

(D) x ((-(r)/(st) + (y/z)) - b

(E) None of these

I got (A) (-bsty - rxy + brz)/(sty - rz), is this the correct answer?

Answer 1

st/r + x/(a + b) = z/y

x/(a + b) = z/y - st/r

x/(a + b) = (rz - sty) / ry

(a + b)/x = ry/(rz - sty)

a + b = xry/(rz - sty)

a = xry/(rz - sty) - b