Helpp I need help like actual help if you can help I appreciate you soo much

Add the two expressions 3.8b - 7 and 2.9b + 9 enter your answer in simplified form

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¯¯¯¯¯¯¯¯)?

Ill mark the brainliest if you me with the these three questions 7,8,9