Roberto has 20 crayons. 12 crayons are red. the rest are blue or yellow. he has two more blue crayons than yellow. how many yellow crayons does he have?

Danielle earns a 7.25% commission on everything she sells at the electronics store where she works. she also earns a base salary of $750 per week. what were her sales last week if her total earnings for the week were $1,076.25?

Ageologist had two rocks on a scale that weighed 4.6 kilograms together.rock a was 0.5 of the total weight.how much did rock a weigh?

How many sides does a regular polygon have if each exterior angle measure is 45 degrees explain your answer, i really don't understand this.