Answer:
d=2
Step-by-step explanation:
SHOWN BELOW
The first equation is

The second equation is

If you sum the two equations you'll cancel y:

And since the sum must be 11, we have y=9.
1.29 is 6.45 divided by 5
The slope is -2.5 because you subtract 2y from both sides, then add two to both sides, then divide both sides by 2 to isolate y