Respuesta :

Subtract the equations

   x  +   y   = 3.5
-3x   -y     = -2.5
-----------------------
-2x + 0  =  1


Solve for x
-2x = 1
x = 1/(-2) = -1/2 = -0.5

Sub into 1st equation:
-0.5 + y  = 3.5
y = 3.5 + 0.5 = 4

Solution = (-0.5,4)