Work out the value of a2-4a
when
a = 10

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¯¯¯¯¯¯¯¯)?

Apositive number a or the same number a increased by 50% and then decreased by 50% of the result?

Can someone check if i did this correct. it’s number 4 if you’re wondering.