What is the number one added the number three?

Scrub a dub toothbrushes are $4.00 each. there is a 10% discount, but there is also a 6% sales tax after the discount is applied. what is the new price after tax? round to the nearest penny

[10 points, algebra 2]according to my answer key the restrictions are -1 and 4. but why not positive 1?

Edger needs 6 cookies and 2 brownies for every 4 plates how many cookies and brownies does he need for 10 plates