so you multiply 5 and 9 which is 45- 10 which is 35 but then its 5-(-2) which when doing this a variable minus a negative makes it a positive so then its 5+2 which is 7 then you have 35/7 or 5
$50 corresponds to 4 kg
That means there must be a number that when you multiply by 4 you get 50.
Let that number be k. k is the price of cheese per kg.
1 kg: y = k * 1
2 kg: y = k * 2