Question 1159602
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(1) From the second given equation, C = 4D.<br>
(2) Add the last two given equations to get A+B+C+D = 12.  Then since the first equation tells us A+B=10, we know C+D = 2.<br>
(3) Now substitute the result from (1) in (2).  4D+D = 2.  D = 2/5.<br>
Once you have the value of that one variable, it will be easy to find the values of the others.<br>