X must be increased by 6 to get its value to be 0. Then the corresponding change in y will be (-2/3)*6 = -4. That value added to -5 makes it -9.
The y-intercept will be -9.
Rational: Any number that can be expressed as a fraction (or a ratio.)
Irrational: Not rational, any number that can't be written down as a fraction. Some examples include

,

, and so on.
Answer: Non-proportional
Step-by-step explanation:
The unit rate for the gas per gallon is $3.17. You want to find out if that is equal to the amount you would pay for 10 gallons at once. If you multiply the unit rate by ten, you would get 10 gallons = $31.70
So...you know that it is not proportional
Remark
You are dealing with a right angle triangle. You can use one of Sin(x) Cos(x) or Tan(x). Since the Hypotenuse is involved and since you are given the adjacent side, Cos(71) is what you will need.
Solution
H = BC
Cos(x) = adjactent / hypotenuse
Cos(71) = 6.3 / H Multiply both sides by H
H * Cos(71) = 6.3 Divide by Cos(71)
H = 6.3 / cos(71) Cos(71) = 0.32557
H = 6.3 / 0.32557 Divide
H = BC = 19.351 Answer
The numbers -9 and -4
Hope this helped :)