You first have to open the equation ie 3a + 4.5 = -1.5. you then group like terms that is 3a = -1.5 - 4.5. This gives you 3a = -6. You then divide both side by the number attached to the variable 'a' ie 3. Which is 3a/3 = -6/3 making a = -6/3 which gives you a = -2
