Can anyone help me solving this question

Write numerical coefficient of y² in the expression 2x² - 15xy – 7y²

Tim's phone service charges $23.06 plus an additional $0.22 for each text message sent per month. if tim's phone bill was $28.56, which equation could be used to find how many text messages, x, tim sent last month?

Find the slope of the line passing through a pair of points