Justin is considering two websites for downloading music. the costs are detailed here.
website 1: a yearly fee of $30 and $1.50 for each download
website 2: $2 for each download
what is a system of equations to represent the costs for one year?
express your equations in the form of y=mx+by=mx+b where x is the number of downloads for the year and y is the total cost for the year.
website 1:
website 2:

Find the missing part. use an improper fraction for your answer.

If m∠abc = 70°, what is m∠abd? justify your reasoning.  using the addition property of equality, 40 + 70 = 110, so m∠abd = 110°.  using the subtraction property of equality, 70 − 30 = 40, so m∠abd = 30°.  using the angle addition postulate, 40 + m∠abd = 70. so, m∠abd = 30° using the subtraction property of equality.  using the angle addition postulate, 40 + 70 = m∠abd. so, m∠abd = 110° using the addition property of equality.

How many quarts of a 50% solution of acid must be added to 20 quarts of a 20% solution of acid in order to get a 40% solution of acid?