Traffic engineers study how long the yellow light for a traffic signal should be, For one intersection. The number of seconds n required for a yellow light is related to the average approach speed v, in feet per second, by the fowllowing. v is 45.

14

step-by-step explanation:

14 x 3 = 42

a 4/6 = 9/12   not proportional

step-by-step explanation:

to find which are not proportional, we can use cross products

if it is true, they are proportional.   if it is not true, they are not proportional.

a 4/6 = 9/12

4* 12 = 6*9

48 = 54

not this is not proportional  

b 2/3 = 12/18  

2* 18 = 3 * 12

36 = 36

this is proportional

c 5/4 = 10/8  

5*8 = 4*10

40 = 40

this is proportional

d 7/5 = 35/25

7*25 = 5 * 35

175 = 175

is proportional

b

step-by-step explanation:

u take $75 minus $60.the anwer/original($75)multiply by 100