Answer: 100d-12a-18b cents
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Step-by-step explanation:
d dollars = 100d cents
for example, if d = 4, then,
4 dollars = 100*d = 100*4 = 400 cents
So Kim starts off with 100d cents.
She buys 'a' apples, where 'a' is a placeholder for the number of apples. If a = 5, then she bought 5 apples and spends 12*a = 12*5 = 60 cents. In general, she spends 12a cents buying 'a' apples.
Similarly, she spends 18b cents buying b bananas. The letter b is the placeholder for the number of bananas.
Overall, Kim spends 12a+18b cents for buying that amount of apples and bananas. Subtract this expression from 100d to find out how much money she'll have left over.
100d - (12a+18b) = 100d-12a-18b
This left over amount is in cents. If you want to convert to dollars, then you would need to divide by 100.