Need with the equation and step on how to do it

Aline has a slope of 1/4 and passes through point (0.4,-1/2). what is the value of the y-intercept?

If /is a line of symmetry, plot the partner points for the ones shown. noch 6 5 4 -3 -2 -1

The salesperson earns a 5% commission on the first $5,000 she has in sales. the salesperson earns a 7.5% commission on the amount of her sales that are greater than $5,000. this month the sales person had $8,000 in sales. what amount of commission, in dollars, did she earn?