#### Answer

$j=-4$

#### Work Step by Step

In order to solve this algebraic expression, we must isolate the variable. A variable is the letter in the problem (for instance, in the equation x+2=10, x is the variable). Because addition and subtraction are inverse operations (they cancel each other out), we know we must add when a number is being subtracted from the variable and subtract when a number is being added to the variable.
In the equation $ j-3=-7$ we must get rid of the 3, which is on the same side as j, in order to solve. Thus, we add 3 on both sides of the equation to find that $j=-4$. We plug -4 in for j and confirm that our answer is, indeed, correct.