(2) A certain brand of tea bags comes in packages of 5, 10, and 20 sachets, costing $5, $9, and $15 per package, respectively. A store sold 16 packages containing a total of 165 sachets and took in...

(2) A certain brand of tea bags comes in packages of 5, 10, and 20 sachets, costing
$5, $9, and $15 per package, respectively.
A store sold 16 packages containing a total of 165 sachets and took in $140.
(a) Write a system of equations to match the description of the information given.
(b) Determine how many packages of each type were sold using the ??????? ??????.