Which of the following gives an example of a set that is closed under addition.
a) the sum of a perfect square and a perfect square.
b) the sum of a prime number and a prime number.
c) the sum of a negative number and a negative number.
d) none of these are an example of the closure property.

option: d is correct

step-by-step explanation:

second option

step-by-step explanation:

the measures of a triangle equal 180. use that to find x.

2x+3x+4x=180

9x=180

9x/9=180/9

x=20

now you know x, you know angle a is 40°, angle b is 60°, angle c is 80°.

because angle a is 40°, the first option doesn't work.

because angle b is 60°, the second option does work.

when you add angle a and b, you get 100°. complementary means it equals 90°, so the third option doesn't work.

when you add angle a and c, you get 120°, which is not 100.

-1   1/6.   you dont subtract the denominators

step-by-step explanation: