Plz answer I will mark u brainiest

The multiplication property of zero states that the product of any number and 0 is 0. what must be true about either a or b to make ab=0

The perimeter of an equilateral triangle is 4 cm more than the perimeter of a square and the length of a side of the triangle is 8 cm more than the length of a side of the aware. find the length of a side of the equilateral triangle

Can someone show me step by step how to do this?