What is the percentage change of 50 to 35 pounds

Tim's phone service charges $26.39 plus an additional $0.21 for each text message sent per month. if tim's phone bill was $31.64, which equation could be used to find how many text messages, x, tim sent last month?

The ph level of a blueberry is 3.1 what is the hydrogen-ion concentration [h+] for the blueberry

What is the equation of a line passing through (-6,5) and having a slope of 1/3