6.7 = 5.2x + 12.3
Subtract 12.3 from each side :
-5.6 = 5.2x
Divide each side by 5.2 :
x = -5.6 / 5.2 = -1.0769... (rounded)
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I've seen the same problem posted here earlier, but
the left side there is 6.7x not 6.7 .
I'm guessing that either that one or this one is copied wrong.