A fitness center has two membership plans. One has a low dollar sign up fee of $15 and costs $38 per month. A second plan has a higher sign up fee of $78, but a lower monthly fee of $31. For what number of months will the cost be the same.

46 dollars is the answer.

step-by-step explanation:

6*6 = 36,         36+10=46

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