Slope intercept form? Again

Answer this question: What is the air temperature when the velocity of sound is 348m/s?

Details: First point on the graph: (6,335) second point: (16,341)
x axis is temperature, y axis is velocity(m/s)
the slope is 0.6 or 3/5 (whichever you prefer)
please explain how you got it.

This is the 4th time I've asked this question, please someone help!?

Slope-intercept form: y= mx+b
Point-slope form: (y-y1)= m (x-x1)

Using the point (6,335)
x1= x-intercept= 6
y1= y-intercept= 335

Plug in the point-slope form:
(y-335)= 3/5 (x-6)
y-335= 3/5x -18/5
y= 3/5x + 331.4

Now apply (if y is 348, then what is x?)
Plug into equation we just created:
y= 3/5x + 331.4
348= 3/5x +331.4
16.6= 3/5x
x= 83/3 That is the air temperature (when you divide the fraction, you get 27.66666; the six repeats)