Aline is written in standard form ax+by=c where a does not =0 find the x-coordinate of the point on the line at which y=3

  x = (c -3b)/a

Step-by-step explanation:

Substitute 3 for y and solve for x.

  ax +b·3 = c

  ax = c -3b . . . . . . . subtract 3b

  x = (c -3b)/a . . . . . divide by the x-coefficient

the answer is 31.27mph