How are you ignoring this fundamental thing we're saying over and over and over and over again???
A/B(C+D) IS NOT EQUAL TO A/B*(C+D)
In your example, using the exact equation you gave:
Equation: A/B(C+D)
Substitution: 10/20(30+40)
Simplification: 10/20(70), and since parenthesis are solved first, it's 10/140
Solve: 1/14 = .071
