please help me fully understand this

Question

EZ clean company has determined that if it spends $30000 on advertisement it can hope to sell 12000 of its minivac a year , but if it spends $50,000 it can sell 16000. write an equation that gives a relationship between the number of dollars spent on advertisement (x) and the number of minivacs sold (y)

Answer 1

set the equation as y= ax +b, so you get two equations,
12000=  30000x+ b
16000 = 50000x + b
solve for a and b, you get a=0.2 d b = 6000
so the equation is y = 0.2x +6000