Solve by factoring. Check your answer.

Please show all your work and explain all steps. Thanks :)

Which multiplicative property is being illustrated below? (type commutative, associative, or identity) 5 × 2 × 4 = 2 × 5 × 4

Arley is building a model of a city map. in one part of the city, three roads form a right triangle, which harley draws as triangle abc, with the following measures: m∠b=90° and m∠a=30°. in his scale model, the hypotenuse of triangle abc, ac¯¯¯¯¯¯¯¯, has a length of 817−−√ cm. what is the value of a (the length of bc¯¯¯¯¯¯¯¯)?

Ineed with question three. i don't understand how i'm supposed to achieve 3 marks.