Just need the answers and work for these two problems so much if u can : )

Mat bought a phone for $100. he has to pay $30 per mouth. if he has paid $640 in total, how many mouth has he had the phone?

Ateacher brought a pack of 17 batteries . each calculator uses 3 batteries . how many calculator can the teacher fill with batteries

What is the equation of the line that is parallel to the line with the equation y= -3/4x +1 and passes through the point (12,-12)