Can someone help? and explain

For f(x)=2x+1 and g(x)= x^2 -7, find (f•g)(x)

For each proportion find the unknown number x 1/5/8=×/15

(c) the diagram shows the first three shapes of a matchsticks arrangement. first shape = 3second shape = 5third shape = 7given m represents the number of matchstick used to arrange the n'th shape.(i) write a formula to represent the relation between m and n. express m as the subjectof the formula.(ii) 19 matchsticks are used to make the p'th shape. find the value of p.