Can someone please explain to me how to solve this problem? I have the answer already all I need is to know how to solve the problem.

Kapil needed to buy a long wooden beam. he went to two sawmills that each charge an initial fee plus an additional fee for each meter of wood. the following equation gives the price (in dollars) of a wooden beam from the first sawmill as a function of its length (in meters). p = 5+20xp=5+20x

If you are trying to move an attached term across the equal sign (=), what operation would you use to move it?

Solve this riddle: i am an odd number. i an less than 100. the some of my digit is 12. i am a multiple of 15. what number am i?