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 q+13=4, we must get rid of the 13 which is on the same side as q, in order to solve. Thus, we subtract 13 on both sides of the equation to find that q=-9. We plug -9 in for q in our original equation and confirm that our answer is, indeed, correct.