Mark is 11 years older than his sister. in 8 years he will be twice as old as she will be then. how old are they now

Sum is 17 and their difference is 3

If f(x) = x+8 and g(x) = 4x- 3, find (f+g)(x)

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?