<PRE><B>Question 593</B>
Start by adding 7d to both sides of the equation.
 
4 = 13 + 3d  (Remember that -4d + 7d = 3d)
 
Then sebtract 13 from both sides to get:
-9 = 3d  (Remember that 4 - 13 = -9)
 
Then divide both sides by 3 and you get:
-3 = d
 
This answer does work in the original problem.
4 - 7(-3) = 13 - 4(-3)
4 + 21 = 13 + 12
25 = 25
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