Sally is three times as old as Sam. The sum of their ages is 84. How old is Sally?

126

Step-by-step explanation:

Sally is 63

Step-by-step explanation:

Represent Sally's age by x and Sam's by  y.

Then x = 3y and x + y = 84.

Substituting 3y for x in the second equation, we get:

3y + y = 84, or 4y = 84, or y = 21.  Since Sally is 3 times as old as Sam, we multiply 21 by 3:  Sally's age is 3(21 years) = 63 years

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