Answer:
-42
Step-by-step explanation:

y=1x+6, because the formula is y=mx+b.
Miss Blue's gross pay is 903.75 dollars.
=> the rate of the Social Security is 7.65%.
Now, let's solve for the amount that the employer should withhold from her salary.
=> 903.75 dollars * .0765 = 69.137 dollars will be deducted to her salary.
=> 903.75 dollars - 69.137 dollars = 834.61 dollars is the remaining of her salary.
I don't feel like working it out/ maybe someone will give you the answer/ but basically you would set

and add it to

to equal 180( which is the degree of a line
so it looks like this:

and then solve( tell me if you need more clarification)
The answer to your question is 70