I may be completely missing something but it is my understanding that all corresponding angles must be equal for triangles to be similar. Therefore if I know that two corresponding angles are equal then the two triangles are similar. If AC does not bisect triangle BAD, how would I confirm that trian...

Hi Everyone, Here is Question: John is 20 years older than Brian. Twelve years ago, John was twice as old as Brian. How old is brian. How come if I try to solve the problem by combination instead of substitution, I come up with the wrong answer? Am I not allowed to use combination in this problem fo...