Jim is given $10 every day. if he spends $7 every day and save the rest, how much does he save in 3 weeks

63 dollars
Because if he gets 10 dollars every day there are 7 days in a week so multiply 7x10 to get 70 and if this continues for 3 weeks multiply 70 by 3 to get 210 because he uses 7 dollars every day for three weeks multiply 7 by 21 (for the amount of days in a 3 week period) and you get 147 take 210 and subtract 147 to get 63

63 dollars
because he gets 10 dolars every 21 days by to get 210 dollor. he uses 7*21=147 dollor. his saved money is 210-147=63$