A fish tank contains orange fish and silver fish. After k more orange fish and 2k more silver fish are added, the probability of choosing an orange fish at random is 1313 . What was the probability of choosing a silver fish before any more fish were added?	Choose the correct choice from the following answers
A) 1/4 B) 1/3 C) 1/2 D) 2/3 E) 3/4
Equation (1): o+k=1xo+k=1x   Equation (2): s+2= 
<gadget id="calculator">+2</gadget>
<output>2</output>
2xs+2k=2x   Multiplying the first Equation by 2: 2o+2k=2x2o+2k=2x. Let´s call this last equation, Equation (3): 2o+2k=2x2o+2k=2x   We can subtract Eq (3) −− Eq (2): 2o−s=02o−s=0, and then s=2os=2o.   Then, s/s+o=2o/3o=2/3   The correct answer is letter (2/3).
<result>D</result>
A fish tank contains orange fish and silver fish. After k more orange fish and 2k more silver fish are added, the probability of choosing an orange fish at random is 1313 . What was the probability of choosing a silver fish before any more fish were added?