In a cartesian coordinate system, the horizontal axis is called the x-axis and the axis is called the y-axis.

Tanya has $42 to spend at the dolphin island store. tshirts sell for $7 each and a pair of sunglases sells for $6.tanya buys 3 tshirts. how many pairs of sunglases can she buys with the amount of money she has left

Me. i can't figure out this question. give an explanation too. .

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?