Find the missing side length.

A)10
B)11
C)12
D)13

Step-by-step explanation:

d

10

Step-by-step explanation:

10 because of proportionality

15/21 = x/14 => x = 14*15/21

3/4 ÷ 3/4

step-by-step explanation:

basically divide any proper fraction with itself to fit the criteria.

so if we are using 3/4, then:

3/4 ÷ 3/4 = 1

so 1 is the quotient.

and the numerators for both these fractions is 3.   and if we divide the numerators:

3 ÷ 3 = 1

we see that quotient is equal to our original quotient as well.