What is the name of the shape that has ten sides?

Which triangle congruence postulate or theorem justifies my claim that the steps i made using construction paper and scissors produce an isosceles triangle? was it sss, sas, asa, aas, or hl?

Which shows the correct solution of the equation 1/2a+2/3b=50, when b=30?

Which equation results from adding the equations in this system? x+6y=9 and -x+2y=-15