Question

3. Suppose Max is Mary's older brother. How old are they?

Answer 1

Let max be mary's older brother.

Let max age be y

and mary age be x

Their sum is 8 and difference is 2, so can write:

x + y = 8

and

y - x = 2

Now we add up the two equations:

x + y = 8

-x + y = 2

-----------------

2y = 10

y = 10/2 = 5

Now,

x + y = 8

x + 5 = 8

x = 8 - 5

x = 3

So,

x = 3

y = 5

Mary is 3 years old and Max is 5 years old.