Sierra has one final problem to solve on her math homework. Which of the following equations CANNOT be used to determine the value of x?

1. x + x + 28.4 = 180

2. 180 - 28.4 = 2x

3. 28.4 + 2x = 180

4. 180 + 28.4 = x + x

Astudent must have an average on five test that is greater than it equal to 80% but less than 90% to receive a final grade of b. devon's greades on the first four test were 78% 62% 91% and 80% what range if grades on the fifth test would give him a b in the course? ( assuming the highest grade is 100%)

A+b= 17, ab=70, find the value of |a-b|

Aiko jumped rope for 20 min and stopped at 8: 05 when did she start