Answers

2016-01-25T18:16:06+08:00
-13 + x = 4

Do the inverse property. Because (-13), the numerical coefficient, is negative, which you can say that it's subtraction (sorry, can't explain well) has an inverse property of addition

-13 + x + 13 = 4 + 13
x = 17

Therefore, the answer is 17.

Check:
-13 + 17 = 4
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