What is the slope of -8,0 and -3, 15 please explain to me

What term best describes a line ans a point that lie in the same plane

Afactory adds 3 red drops and 2 blue drops of coloring to white paint to make each pint of purple paint. the factory will make 50 gallons of the purple paint.how many drops of red and blue coloring will the factory need in the 50 gallon batch of purple paint.

Anyone know? will mark brainliest if correct