What is the y intercept of the line?

Present age of man is 45 years, 5 years back his age was 4 times age of his son what is present age of his son?

Astudent must have an average on five test that is greater than it equal to 80% but less than 90% to receive a final grade of b. devon's greades on the first four test were 78% 62% 91% and 80% what range if grades on the fifth test would give him a b in the course? ( assuming the highest grade is 100%)

There is a linear relationship between a salesperson sales and her weekly income.if her sales are $200 her income is $500 and if her sales are 1,200 her income is $600.what is the relationship between sales and income