In a class in which the final course grade depends entirely on the average of four equally weighted 100-point tests, Brad has sc
ored 87, 89, and 78 on the first three. What range of scores on the fourth test will give Brad a C for the semester (an average between 70 and 79, inclusive)? Assume that all test scores have a non-negative value.
Angles B and D are supplementary angles, so if B's angle is 30 degrees, then D's angle at y would be 150, since they have to add to 180. In short, angle y = 150