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What are the measures of ∠a, ∠b, ∠c and ∠d? explain how to find each of the angles. measure need asap

What is this inequality notation? t is less then or equal to 2

(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.