Answer:the Vega's cell phone bill for March is $155
Step-by-step explanation:
Let x represent the number of talk time in minutes that the family uses for a month.
Let y represent the number of text messages that the family sends in a month.
Let z represent the total cost of using x talk time and sending y text messages in a month.
The cell phone plan costs $75 per month including taxes and fees. Any minutes over 1,000 cost $1 per minute,and any texts over 400 cost $2 per text. This means that the total cost of x minutes and y texts would be
z = 75 + 1(x - 1000) + 2(y - 400)
z = 75 + x - 1000 + 2y - 800
z = 75 - 1000 - 800 + x + 2y
z = x + 2y - 1725
Because of a family emergency,the family uses 1,050 minutes and 415 texts in March. The total cost would be
z = 1050 + 2(415) - 1725
z = 1050 + 830 - 1725 = $155