17n+2 is a numerical expression. a: true. b. false

How to do this , and can some one explain

1c) the number 131 is a term in the sequence defined by the explicit rule f(n)=5n-4. which term in the sequence is 131? 2a) write the first four terms of the function f(n)=n^2-1 2b) what is the 10th term of the sequence defined by the explicit rule f(n)=n^2-1 2c) the number 224 is a term in the sequence defined by the explicit rule f(n)=n^2-1. which term in the sequence is 224?

Given the two similar triangles, how do i find the missing length? if a=4, b=5, and b'=7.5 find a'