How to u determine the y intercept?

Using the slope-intercept form, you can find it out.
Slope = 1.25
Y - intercept = ?
y = mx + b
40 = - 1.25(60) + b
40 = - 75 + b
40 + 75 = b
b = 125
So, the y - intercept is (0, 125)

Cthe residual plot for model 1 has a non random pattern and is a good fit for the data

The household makes $424.45