Biff earned $45 working at happy days drive-in he spent 1/3 of this money on gas for his car and 1/5 of it on flowers for his girl friend how much money does he have left for the big date

Could you use punctuations? Those would help a lot.

Ok, you need to find how much money he is left. One method is to find how much money he spent;

$45 at first, spent 1/3 of it, then 1/5 of it.

How much is 1/3?
1/3 * $45 = $15

How much is 1/5?
1/5 * $45 = $9

Total money spent = 9 + 15 = $24
So, money left = 45 - 24 = $21

The second method is finding the fraction he is left;

'Fractions' he used = 1/3 + 1/5 = 8/15
So, fraction left = 1 - 8/15 = 7/15
Hence, money left = 7/15 * 45 = $21

Hope it helped!