What does plus do? i have plus yet i feel like it doesnt do anything

How do i do this? i don’t understand

For the chance to be team captain, the numbers 1-30 are put in a hat and you get two chances to pick a number, without replacement. which formula correctly shows how to find the probability that you choose the number 1 and then 2?

Prove that 16^4-2^13-4^5 is divisible by 11.