EXPLAIN how to do this plz. will mark brainliest. The graph shows the distance, y, in miles, of a moving motorboat from an island for a certain amount of time, x, in hours:

A graph titled Distance Vs. Time is shown with Time in hours labeled on x axis and Distance from Island in miles labeled on y axis. The scale on the x axis shows the numbers 1, 2, 3, 4, 5, 6, 7, and the scale on the y axis shows the numbers 0, 35, 70, 105, 140, 175, 210, 245, 280, 315. The graph shows a straight line joining the ordered pairs 0, 35, and 1, 105, and 2, 175, and 3, 245, and 4, 315.

What is the speed of the motorboat?

35 miles per hour
70 miles per hour
105 miles per hour
315 miles per hour

Asmall (but heavy) particle placed in a glass of water will follow a zigzag motion because the particle will bounce off of the water molecules it meets. this is called brownian motion. a physicist simulates this on a computer, by varying the distance a particle can travel (called the mean free length), on average, before it collides with a water molecule and assigning the change in motion to be one of 8 directions, each with a similar probability. by running the simulated particle (with the same mean free length) many times she determines that it should take 15 seconds, on average, for the particle to fall to the bottom, with a standard deviation of 1.5 seconds. next she lets a real particle fall through a glass of water and finds that it took 18 seconds. what does she conclude, and why?

Find the solution of this system of equation -7x+y=-20 9x-3y=36

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