Ignore a and b but can you help with c and d? Plz I’ll mark you as a brainiest

Select all the correct answers. what is 221,000,000,000,000,000,000 expressed in scientific notation?

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¯¯¯¯¯¯¯¯)?

Can anyone me get through my algebra 2 class? the only class i need to graduate..