13x + 5y = 16
2x - 8y = 20
Multiply the equations;
13x + 5y = 16 [x2]
2x - 8y = 20 [x13]
26x + 20y = 32
26x - 104y = 260
Reverse the signs on one equation;
26x + 20y = 32
-26x + 104y = -260
'-26x' gets cancelled, leaving;
20y = 32
104y = -260
20y + 104y = 124y
32 - 260 = -228
124y = -228
y = -228 / 124
y = -1.84
Substitute in one equation and find 'x'.
Hope this helped! :)