Im having a trouble solving this problem for the past hour. Any suggestions would be really great, thank you.
In a box there are white and black balls. If we choose randomly one ball from the box, the probability to be white is 0,3. If in the box we put two more white balls and we choose randomly one ball, the probability to take a white ball in 0,5. Find how many are the white and how many are the black balls in the box.
$$\frac{^WC_1}{^{W+B}C_1}=0.3\implies 7W=3B$$
$$\frac{^{W+2}C_1}{^{W+B+2}C_1}=0.5 \implies W+2=B$$
Solve the equations.