My age is four times my grandsons age. my son is 11 years younger than my daughter and my daughter is 30 years older than my grandson. the total of our ages is 196 how old am i

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%)