Passes thru (6,-2) and is perpendicular to Y=-1/2X

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The zoo collects $9.60 for every 24 tickets sold. how much will be collected for 400 tickets?

Sam opened a money-market account that pays 3% simple interest. he started the account with $7,000 and made no further deposits. when he closed the account, he had earned $420 in interest. how long did he keep his account open?