Answer:
As you have written
Z Y = 3 X Y,
It means X, Y, Z are collinear points i.e they lie in the same line or line segment.
Locating points X, Y,Z on the line
Two possibilities are possible
1. First Z, then X and then Y on the line or line segment
→ Z X + Y X= Z Y
But Z Y = 3 X Y [ Given]
→ Z X + Y X = 3 X Y
→ Z X = 3 X Y - Y X
→ Z X = 2 X Y ⇒ which is not the result.
2. 2nd Possibility
First Z, then Y and then X on the line or line segment
→ Z X = Z Y + Y X
→ Z X= 3 X Y + Y X [Z Y=3 X Y→(given)]
→ Z X= 4 X Y , Which is the result.
3:1
6:2
24:8
15:5
30:10
hope this helps, have a great day :)
Answer:

Explanation:
We have been given with the quadratic equation 
We have general formula to find the roots of a quadratic equation first we find the discriminant with formula

and after that to find the variable suppose x we have the formula

And general quadratic equation is

On comparing the given quadratic equation with genral quadratic equation we will have values
a=1, b=-7 and c=-6
After substituting these values in the formula we will get

After substituting in the formula to find x we will get

Answer:
Using a rule is direct and not time wasting, which is not the case for listing functions
It seems to me, that if you were to add the price of all three items together, then multiply by 7.5%, you'd have the answer. Remember that 7.5% = .075 ... in other words, that is the number you would multiply the sum of the items by. Does that help?