Use the matrix method to solve

Question

5x+3y=35
3x-4y=-8

Answer 1

http://www.gregthatcher.com/Mathematics/GaussJordan.aspx

in the end
1 0 4
0 1 5

Answer 2

check
20 + 15 = 35
12 - 20 = -8 whew !

Answer 3

another matrix way with determinants
det of
5 3
3 -4 = -20 -9 = -29
for y put column 3 in for col 2
det of
5 35
3 - 8 = -40 - 105 = -145
-145 / -29 = 5 which is y