Price of the rent table: $135
Price of baking supplies: $4.50
Price of one cake: $12
Profit inequality: 12*n > 135 + 4.50*n ...(1)
Where n is the number of cakes Keji sells
3a.
For n = 15
Replacing in (1):
12*15 > 135 + 4.50*15
180 > 202.50
But this inequality is false, so we conclude that Keji will not make a profit if he sells only 15 cakes.
3b.
From (1), we solve the inequality for n:
12*n - 4.50*n > 135
7.5*n > 135
n > 18 ...(2)
From the inequality (2), we conclude that Keji needs to sell at least 18 cakes to make a profit.
3c.
This is explained above