How to make the mark of degree on the calculator ??

most models of scientific calculators in degree mode, all you have to do is press "Mode" and then look at the numbers on the screen beside the menu items. Locate the number beside "Deg" or "Degrees" and press it to change the mode of your calculator

The constant of proportionality is 0.5      

Step-by-step explanation:

We are given the following in the question:

Cost of 25 game tickets = $12.50

Cost of 35 game tickets = $17.50

The cost of ticket C(n) is directly proportion to the number of tickets n.

Thus, we can write:

where a is the constant of proportionality.

Putting values, we get,

Thus, the constant of proportionality is 0.5