Chapter 2 - Solving Equations - 2-1 Solving One-Step Equations - Practice and Problem-Solving Exercises - Page 86: 64

d=-.6

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 2x=10, x is the variable). Because multiplication and division are inverse operations (they cancel each other out), we know we must divide when a number is being multiplied by the variable and multiply when the variable is being divided by a number. In the equation 4d=-2.4, we must get rid of the 4, which the variable is being multiplied by, in order to solve. Thus, we divide both sides by 4 to find that d=-.6. When we plug -.6 into the original equation and simplify, we get that -2.4=-2.4, so the solution is correct.