This question is worded badly, so don't be alarmed.
Obviously if this were a square patter the number of red tiles could only be 1,4,9,16,25,36 etc and this is not the numbers given...It would help tremendously if they gave you another reference point so as to know how the tiles were being laid out.
If they are laid out alongside one another with a consistent border for each you wouldn't need 12 blue tiles for each red tile either...if two were laid side by side you would only need 20 blue tiles to have the border around both...you see how the arrangement makes a huge difference and you are given no details as to what that arrangement is...
So just to keep it simple, assume that each red tile is surrounded by 12 blue tiles....
Total tiles equals r+12r=13r
t=13r so
t(15)=195, t(20)=260, t(25)=325, t(30)=390
First, you would multiply: -13 = 70m - 2m. Then, you subtract the like terms, which would be 70m - 2m: -13 = 68m. You are looking for what m is, so you would divide 68 on both sides: m = - 13 / 68. In math, people would usually like fractions more than decimals, but if you are looking for the decimal number, it would be m ≈ - 0.19.
B. Sandwich costs $7.70 and the soda costs $2.20
