2x-4=7 Identify the constant, coefficient, and variable in each of the following expressions/equations

Ican figure out 20 shares multiply by $117.98 =2359.6920 shares multiply by $124.32=2486.40then take 40 shares multiply by $128.48=5139.20after that i'm lost any be greatly appreciated.

Find the sum of the measure of the interior angles of a polygon of 9 sides ; of 32 sides

The square root of 9x plus 7 plus the square rot of 2x equall to 7