Money made for a sandwich shop was directly proportional to its advertising budget. When the owner spent $2000 a month on advertising, the revenue was $120,000. If the revenue is now $180,000, how much is the owner spending on advertising?

Question

120,000

simplest way: by ratio

2000:120000=x:180000
2/120 = x/180000
120x = 360 000
x = 3000

second way

let revenue be R, let Advertising cost be A
then R = kA, where k is a constant

replace the given case where R=120000 and A = 2000
120000=k(2000)
k = 60 000
so R = 60 000A

sub 180000 for R....solve ... A=3000