3 Find the length of ST to the nearest metre. m2 - 16 6​

Can someone explain the elimination method to me for this problem?

Solve the problem. a student earned grades of c, a, b, and a in four different courses. those courses had these corresponding numbers of credit hours: 4, 5, 1, and 5. the grading system assigns quality points to letter grades as follows: a = 4, b = 3, c = 2, d = 1, and f = 0. compute the grade point average (gpa) and round the result to two decimal places. 3.40 3.50 8.75 2.18

Tanyss's house has 25 windows. her brother has washed 22 of the windows. what percent of the windows has her brother washed?