143 / 6x+12 = 132 / 72
143 / 6x+12 = 11 / 6
crossmultiply:
66x + 132 = 858
66x = 726
x = 11
Add the two values being multiplied by m
37.26 + 2.7 = 39.96
39.96 m + 0.0015 is the most simplified you can get without having a way of finding the value of m. I apologize if I am mistaken, but I'm fairly certain! :)
Where x is the length of the first piece

so the first piece is 3 inches, the second is 6 inches and the third is 19 inches
Becouse k and n are 'neighbours' so their sum are 180
so k=180-42=138