Question

Linda is 12 years younger than her sister Laura. Together their total age is 18. How old is Linda? How old is Laura?

Answer 1

Answer:

Linda: 3 ; Laura: 15

Step-by-step explanation:

Note that Linda + Laura's age is 18, and that Linda is 12 years younger than her sister.

Let "Linda" = x , "Laura" = y:

x + y = 18

x = y - 12

First, plug in y - 12 for x in the first equation:

(y - 12) + y = 18

Simplify.

2y - 12 = 18

Isolate the variable (y). Note the equal sign, what you do to one side, you do to the other. Do the opposite of PEMDAS. First add, then divide.

2y - 12 (+12) = 18 (+12)

2y = 18 + 12

2y = 30

(2y)/2 = (30)/2

y = 30/2

y = 15

Next, plug in 15 for y in the second equation (the other equation would work too).

x = y - 12

x = (15) - 12

x = 3

Linda's age is 3, Laura's age is 15.

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