Solving for D & C
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(3c + d) + (-d) = 60 + (-d)
3c + d - d = 60 - d
3c= -d + 60
3c/3 =-d+60/3
c= -d+60/3
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(3c+d)+(-3c)=60+(-3c)
d = -3c + 60
