Can someone answer this for me please

Will give brainliest sum of arithmetic series (sigma notation) find the numerical answer to the summation given below. (image shown below)

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

What is the anwers for 9+2x=5x-3-x