Use your knowledge on the triangle proportionality theorem to find the missing side length indicated. Be sure to explain the proportion you used.

? = 4.29

Step-by-step explanation:

Remark

Let  x be the question mark. You get the proportionality by using the dimensions of the little triangle to the dimensions of the large triangle.

Equation

14/(14+ 4) = 15/(x + 15)                   Combine like terms on the left

14/18 = 15/(x + 15)                          Cross multiply

14*(x + 15) = 18 * 15                        Simplify the right

14(x + 15) = 270                             Divide by 14

x + 15 = 270 / 14

x + 15 = 19.29                               Subtract 15 from both sides

x = 19.29 - 15

x = 4.29    

the mistake in the pattern is that :

b. the decimal point was moved one too many place values each time

the correct pattern could be made by :

b. moving the decimal point to the right the same numbers of place values as the exponents