Mr. Duck invested 36,000 in two accounts, one yielding 7% interest and the other yielding 12%. If he received a total $3,520 in interest at the end of the year, how did he invest in each account of 7% _____ and 12% _____.

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You need to set up two equations such that:

`{(x + y = 36000),(7%x + 12%y = 3520):}`

x,y represent the investments

`{(x + y = 36000),(7x + 12y = 352000):}`

You may use substitution method to solve the simultaneous equations, such that:

`{(x = 36000 - y),(7(36000 - y) + 12y = 352000):}`

`{(x = 36000 - y),(252000 - 7y + 12y = 352000):}`

`{(x = 36000 - y),(5y = 352000 - 252000):}`

`{(x = 36000 - y),(5y = 100000):} => {(x = 36000 - y),(y = 20000):}`

`{(x = 36000 - 20000),(y = 20000):} => {(x = 16000),(y = 20000):}`

**Hence, evaluating the investments in each account yields that Mr. Duck has invested `$16000` in `7%` account and `$20000` in `12%` account.**

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