A stall was having its grand opening promotion for doughnuts and cookies at the prices as shown. Lynn spent an equal amount of money on the doughnuts and cookies for her company party. She bought 75 more doughnuts than cookies. What was the total number of doughnuts and cookies bought by Lynn?
To make the amount spent on doughnuts and cookies the same, find the LCM of 12 and 9.

LCM of 12 and 9 = 36

Number of sets of $9 in $36
= 36 ÷ 9
= 4

Number of doughnuts that can be bought with $36
= 4 x 6
= 24

Number of sets of $12 in $36
= 36 ÷ 12
= 3

Number of cookies that can be bought with $36
= 3 x 3
= 9

Number of more doughnuts than cookies in every $36 spent on each item type
= 24 - 9
= 15

Number of sets
= 75 ÷ 15
= 5

Number of doughnuts and cookies in 1 set
= 24 + 9
= 33

Total number of doughnuts and cookies that Lynn bought
= 5 x 33
= 165

Answer(s): 165