If we say A = ream of paper and B = cost of ink than we can set-up an expression to calculate when A is equal to a number what the number of B will be.
Maximim of 270$ so anything we buy must be equal to this.
Ream of paper cost 6$ each so 6A represents the number of reams bought since we said A is number of reams of paper.
Ink Cartridges are 18$ each so 18B would represent this based on B = to cost of ink.
Now setting up our equation
6A + 18B = 270
When A = 1
B = 14.67 Ink Cartridges
When A = 1 Ream ofpaper
15=-2(2t-1) -- expand brackets
15=-4t+2 -- subtract 2
13=-4t -- switch signs, best to have a positive variable
4t=-13
t=-13/4
I will give it to you in order 2 5 9 4 10 3 6 7 8 1 10 7 3 9 8 5 1 4 2 6 5 1 3 6 4 9 2 5 7 8
The percent of the discount is 28 percent off
If functions transfer some a to b via some formula, then inverse of such functions transfer b to a via some other formula.
Hope this helps.