## College Algebra (10th Edition)

7x=21 The variable we want to solve for is x. What is being done to x? 7x x is multiplied by 7. To find the original value of x, we must undo what was done to x. To undo multiplication by 7 we can divide by 7. Remember whatever you do to one side in an equation you must do to the other side to preserve the equality. Divide both sides by 7 $\frac{7x} {7}$ = $\frac{21} {7}$ Simplify both sides by dividing numerator and denominator by 7. $\frac{7x} {7}$ = $\frac{x} {1}$ =x, $\frac{21} {7}$ =3 So the equation simplifies to x=3 Check your answer: 7x=21 Replace x with your solution:3 7(3)=21 Simplify 21=21 It checks so the solution (x=3) is good!