Siti has the exact amount of money to buy 84 bottled drinks or 126 canned drinks. She has already spent some of the money to buy 39 canned drinks and 42 bottled drinks. How many more bottled drinks can she buy with the remaining money? Ans: ___

1. Find the equivalent number of bottled drinks for the canned drinks bought.

Since the total money can buy $84$ bottled drinks or $126$ canned drinks, the cost of $126$ canned drinks is equal to the cost of $84$ bottled drinks.
Ratio of canned to bottled drinks for the same cost = $126 : 84 = 3 : 2$.
This means $3$ canned drinks cost the same as $2$ bottled drinks.
Number of bottled drinks equivalent to $39$ canned drinks = $\frac{39}{3} \times 2 = 26$.

2. Calculate the total equivalent bottled drinks bought and the remaining she can buy.

Total equivalent bottled drinks bought = $42 + 26 = 68$.
Remaining bottled drinks she can buy = $84 - 68 = 16$.