More free points because I quit

The price of a box of 15 cloud markers is $12.70. the price of a box of 42 cloud markers is $31.60. all prices are without tax, and the price of the packaging is the same for any size. how much would 50 cloud markers in a box cost? write an equation which will tell the price p for the number n markers in the box.

Asap 25 pts + brainliest to right/best answer

It is given that cs is the perpendicular bisector of segment ab. by the definition of perpendicular we can conclude that angles csa and csb are right angles. which answer choice justifies the fact that ? csb ? ? csa?