Find the area of an equilateral triangle (regular 3-gon) with the given measurement

Which property was used to simplify the expression? 3c+9 +4c=3c+4c+9

Jim had 3,067.48 in his checking account he wrote a check to pay for two airplane tickets. his account now has 1,845.24.

Graph the line with the given slope m and y-intercept b. m=-3,b=1