Evaluate 1/3m - 1 - 1/2n

m=21
n=12

[10 points, algebra 2]according to my answer key the restrictions are -1 and 4. but why not positive 1?

Boris needs to buy plastic spoons. brand a has a box 42 spoons for $2.37. brand b has a box of 72 spoons for $3.57. find the unit price for each brand. then state which brand is the better buy based on the unit price. round your answer to the nearest cent.

Awindow washer cleans 42 windows in 2 hours. at this rate, how many windows did he clean in 180 minutes.