IKMC 2007 - Grades 7-8 - Self-study Question 13

Question 13

Initially $\frac23$ of customers buy A and $\frac13$ buy B. After advertising, $\frac14$ of the former A customers switch to B. What are the new proportions?

$\frac14$ buy A, $\frac34$ buy B
$\frac7{12}$ buy A, $\frac5{12}$ buy B
$\frac12$ buy A, $\frac12$ buy B
$\frac13$ buy A, $\frac23$ buy B