Question 230434
Let x=the number of parts sold
Let y =the profit

Find the slope of the linear equation by using the slope formula:

m=(y2-y1)/(x2-x1)

In this case, y2=$125, y1=$80. x2=40, x1=25.

m=($125-$80)/40-25= $45/15
m=$3/part

We need to find the y-intercept (or b).

y=mx+b

I can choose either point (40,125) or (25,80).

y=mx+b
125=3*40+b
125=120+b
125-120=b
5=b

The line's equation is:

y=3x+5

If profits are $305:

305=3x+5
300=3x
x=100

If profits are $305, 100 parts were sold.

If profits are $905:

905=3x+5
900=3x
x=300

If profits were $905, 300 parts were sold.