## Elementary Algebra

Let x represent the score of the fourth test. Her average will be $\frac{87+81+74+x}{4}$. Because she needs to have an average of 85 or higher for the four tests, we solve the following inequality. $\frac{87+81+74+x}{4}$ $\geq$ 85 Multiply both sides by 4. 87+81+74+x $\geq$ 340 x + 242 $\geq$ 340 x $\geq$ 98 As we can see, she needs to have a score equal to or higher than 98 to achieve an average of 85 or higher for the four tests.