Question 33961
let the first # be x and the second # be y
x - y = -1 -- eq 1
2x + 3y = 13 -- eq 2

multifply eq 1 by 2, yields
2x - 2y = -2 -- eq 3

now, take eq2 - eq3, u will get
0 - 5y = 15
y = -3

sub y = -3 into any of the above equation, 
let use eq1, u will get
x - (-3) = -1
x + 3 = -1
x = -4