Harry used 84% of the money in his savings account to buy a used to it like that costume $1050 i want your money is left in harrys savings account

Are you saying that $1050 was the initial amount of money in the savings account? If so then you'd find 84% of 1050, which is 1050*.84. (.84 is the decimal version of 84%)

Question not clear, it could be: he spend 84% which was $1050 or He spend 84% of 1050, 2 answer below

ANSWER 1
if he spend 84% of 1050 then he has 100-84=16% left
percnet means parts out of 100 so
16%=16/100=1.6/10=0.16
'of' means multiply so
0.16 times 1050=168
he had 168 dollars left

OR

ANSWER 2
so if he spend 84% of his money to buy a costume and he spend 1050
84%=1050 so solve for remaining
remaining=100-84=16%

if 1050=84% then solve for 16%
so set up a ratio and proportion
1050/84%=x/16% so therefor
(note: equivilent fracitons when multiplied make 1/1 so exg 1/4=2/8 so 1/4 times 8/2=8/8=1)

so 84%/1050 times x/16%=1=84x/16800
1=84x/16800
multiply boht sides by 16800
16800=84x
divide both sdies by 84
200=x
$200 left in bank account

Iam thinking the answer is a.) knew