Consider u = {x|x is a positive integer greater than 1}.

which is an empty set?

{x|x ∈ u andone-half is prime}
{x|x ∈ u and 2x is prime}
{x|x ∈ u andone-half can be written as a fraction}
{x|x ∈ u and 2x can be written as a fraction}

It's B

Step-by-step explanation:

I just took the test and got it right. :D

step-by-step explanation:

ok so im not 100% sure but you would start by adding 5.1t and 1.9t beacuse they have the same variable. that is 7t.   then add -3.6 + 1.2 which is -2.4

so then keep that as -2.4 + 7t. i apologize if this is incorrect. best luck on your test < 3