Question

I really need help with this question:

In a group of 14 children some are nine years old and the rest are eleven years old. When the ages of the 14 children are added together their total is 138 years. How many nine-year-old children are there?

Answer 1

Therefore, there is 8 children that is 9 years old and 6 children that is 11 years old.

Explanation:

Let x be the no. of 9 years old and y be the no. of 11 years old.

x+y= 14 (1)

9x+11y= 138 (2)

From (1) :

x=-y+14 (3)

sub (3) into (2) :

9(-y+14)+11y= 138

-9y+126+11y=138

2y= 138-126

y= 6 (4)

sub (4) into (1) :

x+6= 14

x= 8