Answer:
The answer to your question is below
Step-by-step explanation:
Data
Center = (0, 0)
Vertex = (13, 0)
Focus = (12, 0)
Process
From the data we know that it is a horizontal ellipse.
1.- Calculate "a", the distance from the center to the vertex.
a = 13
2.- Calculate "c", the distance from the center to the focus
c = 12
3.- Calculate b
Use the Pythagorean theorem to find it
a² = b² + c²
-Solve for b
b² = a² - c²
-Substitution
b² = 13² - 12²
-Simplification
b² = 169 - 144
b² = 25
b = 5
4.- Find the equation of the ellipse
or 
Answer:
18
Step-by-step explanation:
Sum the parts of the ratio, 3 + 4 = 7
Divide the amount of marbles by 7 to find the value of one part of the ratio
42 ÷ 7 = 6 ← value of 1 part of the ratio, thus
red marbles = 3 × 6 = 18
The answer is 13/85. You could find out the answer by doing the reprical multiplication.