Given:
Expression is

To prove:
If r is any rational number, then
is rational.
Step-by-step explanation:
Property 1: Every integer is a rational number. It is Theorem 4.3.1.
Property 2: The sum of any two rational numbers is rational. It is Theorem 4.3.2.
Property 3: The product of any two rational numbers is rational. It is Exercise 15 in Section 4.3.
Let r be any rational number.
We have,

It can be written as

Now,
3, -2 and 4 are rational numbers by property 1.
is rational by Property 3.
are rational by Property 3.
is rational by property 2.
So,
is rational.
Hence proved.
Answer:
A
Step-by-step explanation:
Angle 3 and angle 6 are congruent because they are alternate interior angles. Angle 3 plus angle 1 is 180 degrees. So you just subtract 123 from 180 (180-123) and you get 57 degrees.
Sally paints at a rate of 1/7th room / hour
Steve paints at a rate of 1/6th room / hour
If they both painted together, they would paint 1/7 + 1/6 = 13/42 room/hour
so to paint the whole room, it would take 1/(13/42) = 42/13 =
<u>
3.23 hours (3 significant figures)</u>