The row-echelon form of the augmented matrix of a system of equations is given. Find the solution of the system. 1 0 -5 -3
0 1 -4 -5
0 0 0 0
x=
y=
z=
t= any real number

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%)