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 d-2=5.5, we must get rid of the 2, which is on the same side as d, in order to solve. Thus, we add 2 on both sides of the equation to find that d=7.5. We plug 7.5 in for d and confirm that our answer is, indeed, correct.