Hi, there can someone me with numbers 1 and 2 how to prove that what there saying is correct

Which expressions are equivalent to k/2 choose 2 answers: a k-2 b 2/k c 1/2k d k/2 e k+k

Julie begins counting backwards from 1000 by 2’s and at the same time tony begins counting forward from 100 by 3’s.   if they count at the same rate, what number will they say at the same time?

If f(x)=3 over x+2 - square root x-3 then f(7)=