HELP!
I need this for a test in Math

If chord ab is congruent to chord cd, then what must be true about ef and eg?

In the diagram below,abc is congruent to dec what is the value of 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%)