How to Correctly Solve the Circuit with Supernode Equations?

[unkown]

Homework Statement

http://piazza.com/view/gsqhumgwtax

Homework Equations

The Attempt at a Solution

I got everything right except in Q4 matrix (second equation 2nd and 3d slots)

my supernode equation is
I got this equation. Going clockwise
= -12+75(I1-I3)+14(I2-I3)+49(I4)=0
3048 = 75I1 + 14 I2 + 49I4

can anyone see what am i doing wrong

 

[gneill]

What happened to the 34V source that follows the 39 Ohm resistor in the loop?