Sarah has a brother who is 5 years younger than herself and another brother who is 8 years younger than herself. She observes that the product of her brothers ages is equal to the age of her 40 year old father. How old is Sarah? How do we setup an equation for this using null factor law presumably.

Sarah is 13 years old

Step-by-step explanation:

Represent Sarah's age with S

Her first brother's age with F

Her second brother's age with B

So, we have:

From the first statement, we have:

---- (1)

From the second, we have:

---- (2)

The product of their ages is 40.

First, we make F the subject in (1) and B the subject in (2)

Their product is represented as follows:

Substitute values for F and B

Open bracket

Subtract 40 from both sides

Factorize:

Split:

or

But Sarah's age can't be 0 because she has two younger brothers.

So, we stick to

Make S the subject

Hence, Sarah is 13 years old

look a the sides they are perpendicular

$450 is the answer.

step-by-step explanation:

30% of 450 = 135

450-135=315