(15 + 9) + 13 = 15+ (9 + 13)

Mary used 1/7 of a spool of ribbon to complete 4 projects. she used the same amount of ribbon on each project. how much ribbon did she use on each project?

What does x = in this equation x+3+2x=x+5

Joline is solving the equation 0=x^2-5x-4 using the quadratic formula which value is the negative real number solution to her quadratic equation round to the nearest tenth if necessary